Elements and their symbols: the alphabet of everything
By the end of this lesson you will be able to
- Define an element as a substance made of one kind of atom, and state how many are known and how many occur naturally.
- Write and read chemical symbols, including the ones taken from Latin names (Na, K, Fe, Pb, Au, Ag, Sn, Hg, W), and explain the rules Berzelius set in 1813.
- Describe the physical and chemical properties that separate metals, non-metals and metalloids, and classify an unfamiliar element from its properties.
- Explain, at the level of particles, why metals conduct heat and electricity and why most non-metals do not.
- Locate the metals, non-metals and metalloids on the periodic table and describe the staircase line that separates them.
The puzzle
Everything you can touch — the phone in your hand, the water in a Gaborone tap, the diamond from Jwaneng, your own body, the Sun — is made from a set of just 94 natural ingredients, and most of it from fewer than twenty. A pharmacist in Tokyo, a miner in Selebi-Phikwe and a chemist in Berlin all write “Fe” for iron, though they say “tetsu”, “tshipi” and “Eisen”. Who decided that the alphabet of the universe would have 118 letters, and why does the letter for gold come out as “Au”?
Predict which of these are elements and which are not: gold, water, salt, oxygen, steel, diamond, air, sulfur, brass, mercury. Then predict which of the elements on your list are metals.
Compare your answer
Elements: gold, oxygen, diamond (pure carbon), sulfur, mercury. Not elements: water (hydrogen + oxygen, a compound), salt (sodium + chlorine, a compound), steel (iron with a little carbon, a mixture), air (a mixture of nitrogen, oxygen and more), brass (copper + zinc, a mixture). Metals among the elements: gold and mercury — yes, mercury is a metal even though it is a liquid at room temperature. Diamond is hard and shiny but it does not conduct electricity and it shatters rather than bends: a non-metal. This lesson gives you the tests that settle the argument.
The science — structured notes
1.1 What an element is
An element is a substance made of only one kind of atom. It cannot be split into anything simpler by heating it, dissolving it, passing electricity through it or reacting it with something else — a chemist can turn iron into rust or into steel, but never into anything that is not iron. A compound is two or more elements joined by chemical bonds in a fixed ratio (water, H₂O, is always two hydrogens to one oxygen); a mixture is substances that are together but not joined (air, steel, sea water) and can be separated by the methods you met in Year 1.
| How many elements? | Number | Notes |
|---|---|---|
| Known and named | 118 | From hydrogen (1) to oganesson (118), the last named in 2016 |
| Occur naturally on Earth | 94 | Hydrogen to plutonium; a few of these (technetium, promethium, francium) exist only in traces |
| Made only in laboratories | 24 | Elements 95–118, made a few atoms at a time by smashing nuclei together (Lesson 4.5) |
| In your body, in useful amounts | about 25 | Oxygen, carbon, hydrogen and nitrogen make up 96 % of your mass; calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium most of the rest |
| In a smartphone | about 70 | Copper, silicon, lithium, cobalt, gold, indium, tantalum, and a row of rare-earth metals in the speaker magnets |
1.2 Symbols — Berzelius’s rules and the Latin survivors
Every element has a symbol of one or two letters. The rules were set by the Swedish chemist Jöns Jacob Berzelius in 1813 and have not changed since:
| Element | Symbol | Latin name | Where the Latin comes from |
|---|---|---|---|
| Sodium | Na | natrium | natron, the soda mined in Egypt for making glass and for embalming |
| Potassium | K | kalium | Arabic al-qalī, the ash of burnt plants — the origin of the word alkali too |
| Iron | Fe | ferrum | the Roman word for the metal of swords and ploughs |
| Lead | Pb | plumbum | Roman water pipes were lead — hence “plumber” |
| Gold | Au | aurum | “shining dawn” |
| Silver | Ag | argentum | “white, shining”; Argentina is named for it |
| Tin | Sn | stannum | the Roman word for the metal mixed with copper to make bronze |
| Mercury | Hg | hydrargyrum | Greek “water-silver”: the liquid metal |
| Tungsten | W | wolfram | German “wolf’s foam”, from the ore that “ate” tin during smelting |
| Copper | Cu | cuprum | from Cyprus, the Roman source of copper |
| Antimony | Sb | stibium | the black eye-paint of ancient Egypt |
Decide what each of these means: Co, CO, Ca, C, Cs, CS₂.
Co — cobalt, one element (capital then small).
CO — carbon monoxide, a compound of two elements, carbon and oxygen (two capitals means two symbols).
Ca — calcium; C — carbon; Cs — caesium. Three different elements sharing a first letter, which is exactly why the second letter is needed.
CS₂ — carbon disulfide, a compound: one carbon, two sulfur. Reading a formula is reading symbols one capital letter at a time.
1.3 Metals, non-metals and metalloids
About 80 % of the elements are metals. What makes a metal is a set of properties that come together because of how the atoms are held: in a metal, the outer electrons of every atom are free to move through the whole solid, a “sea” of electrons around a lattice of positive ions. Almost every property in the table below follows from that one fact.
| Property | Metals | Non-metals | Why (particles) |
|---|---|---|---|
| Electrical conduction | Good conductors | Poor (insulators) — except graphite | Free electrons carry charge through a metal; in a non-metal the electrons are fixed in bonds |
| Thermal conduction | Good | Poor | Free electrons carry energy from the hot end fast; non-metals rely only on slow vibrations passed between atoms |
| Malleable / ductile | Can be hammered into sheets and drawn into wires | Brittle when solid — they shatter | Layers of metal ions slide over each other and the electron sea keeps them bonded; in a non-metal the bonds break when the atoms move |
| Lustre (shine) | Shiny when freshly cut or polished | Dull — except iodine and diamond | Free electrons reflect light |
| Melting and boiling points | Mostly high (iron 1538 °C, tungsten 3422 °C) | Mostly low; eleven are gases at room temperature | Strong forces hold metal ions together; many non-metals are small molecules with weak forces between them |
| Density | Mostly high (iron 7.9, gold 19.3 g/cm³) | Low (sulfur 2.1 g/cm³; gases far lower) | Metal atoms pack tightly |
| Sound when struck | Sonorous — they ring | Dull thud | The ordered lattice carries vibrations |
| Oxide | Basic — neutralises acids; dissolves (if soluble) to give an alkali | Acidic — dissolves to give an acid | Metal oxides contain oxide ions that accept hydrogen from acids; non-metal oxides react with water to make acids (CO₂ → carbonic acid, SO₂ → sulfurous acid) |
| State at room temperature | Solid (except mercury) | Solid, liquid (bromine) or gas | — |
Between the two families sit the metalloids (semi-metals): boron, silicon, germanium, arsenic, antimony, tellurium. They look like metals — grey and shiny — but are brittle and conduct electricity only a little, and only when warmed or when a trace of another element is added. That in-between conduction is why silicon runs every computer chip on Earth: a material that can be switched between conducting and not conducting is a switch, and a billion switches on a fingernail is a processor.
Element X is a grey, shiny solid. It conducts electricity well, is easily bent into a wire, has a density of 8.9 g/cm³, and its oxide dissolves in water to give a solution with pH 12. Classify it and justify each step.
Shiny and grey — could be metal or metalloid, so this alone is not enough.
Conducts electricity well and bends into wire — metals do both; metalloids conduct poorly and are brittle. Strong evidence for a metal.
Density 8.9 g/cm³ — high; typical of a metal (this is copper’s density, though copper is not grey — nickel and cobalt are both 8.9 and grey).
Oxide gives pH 12 — alkaline, so the oxide is basic, the chemical test for a metal. X is a metal. Every property agrees; state them all, because one property could be an exception.
1.4 Where they sit on the table
Open a periodic table and draw a staircase line starting between boron (B) and aluminium (Al) and stepping down to the right, ending between polonium (Po) and astatine (At). Everything to the left of the line is a metal — the great majority of the table, including all the tall columns on the left and the whole central block. Everything to the right and above is a non-metal — a small triangle in the top right corner, plus hydrogen, which sits at the top left because of its single electron but is a gas and a non-metal. The elements touching the line on either side are the metalloids. Read the table like a map: metals west, non-metals north-east, the staircase is the coast.
| Region of the table | What lives there | Examples |
|---|---|---|
| Far left columns (Groups 1 and 2) | Soft, very reactive metals | Li, Na, K · Mg, Ca |
| Central block (transition metals) | Hard, dense, high-melting metals — the ones we build with | Fe, Cu, Ni, Cr, Ti, Au, Ag, Pt |
| Along the staircase | Metalloids | B, Si, Ge, As, Sb, Te |
| Top right triangle | Non-metals | C, N, O, F, P, S, Cl, Br, I |
| Far right column (Group 0 / 18) | Noble gases — unreactive non-metals | He, Ne, Ar, Kr, Xe, Rn |
| Top left, alone | Hydrogen — a non-metal placed by its one electron | H |
1.5 Testing an unknown: what to measure
Given a lump of an unknown element, a chemist runs the tests in this order — cheapest and safest first.
Write the symbol for each element, and say whether it is a metal, a non-metal or a metalloid.
(a) Potassium, lead, silicon.
(b) Tungsten, bromine, silver.
(c) A student writes the symbol for cobalt as CO. Explain what is wrong and what CO actually means.
Reveal answer
(a) K (from kalium) — metal; Pb (plumbum) — metal; Si — metalloid, on the staircase.
(b) W (wolfram) — metal, the highest-melting of all; Br — non-metal, a liquid; Ag (argentum) — metal.
(c) The second letter of a symbol must be small: Co. Written CO it reads as two symbols, C and O — carbon monoxide, a compound and a poisonous gas. The capital letter is what separates one element from the next in a formula.
“Every metal is a solid, and every solid that conducts electricity is a metal.”
Reveal answer
False, twice. Mercury is a metal and a liquid at room temperature (it melts at −39 °C), and caesium and gallium melt in your hand. Graphite is a solid that conducts electricity well — the free electrons between its layers of carbon atoms carry current — but it is a non-metal: brittle, dull-black, with an acidic oxide (carbon dioxide). Classification needs the whole set of properties, and the oxide test is the one that does not lie.
“Steel is an element because it is made of iron, and iron is an element. Water is an element because you cannot see anything else in it.”
Reveal answer
Steel is a mixture of iron with a small percentage of carbon (and often chromium, nickel or manganese); it contains more than one kind of atom, so it is not an element, even though its main ingredient is. Water is a compound: every molecule has two hydrogen atoms bonded to one oxygen atom, and it can be split into those two elements by passing electricity through it — which no element can be. “You cannot see anything else” is not the test; the test is whether it can be broken into simpler substances by chemical means.
What if Berzelius had written in English rather than Latin? Which of the eleven Latin-symbol elements would have different symbols today, and what problem would that have caused with the element that is now “S”?
Reveal answer
Sodium would probably be So or Sd, potassium Po or Pt, iron I or Ir, lead L or Le, gold G or Go, silver Si or Sv, tin T or Ti, mercury M or Me, tungsten T or Tu, copper C or Cp, antimony A or An. Almost every one clashes with an existing symbol: Po is polonium, Pt platinum, I iodine, Ir iridium, Si silicon, Ti titanium. Sulfur would keep S, but silver, silicon and sodium would all be competing for it. Latin was not chosen for elegance; it was the one language every European chemist could read, and a fixed dead language does not change its spellings — a good property for a code that must last centuries.
Try it — metals and non-metals conducting heat
The clearest single difference between a metal and a non-metal is how fast heat travels through it. Clamp a rod with one end in a flame and a blob of wax on the other end, and time how long the wax takes to drop. Run copper, steel, glass, plastic and wood at the same length, then change the length for one material. The metals should stand out by a factor of ten or more — and the reason is the same free electrons that carry a current.
Suppose your results for 15 cm rods with 2 g of wax were: copper 10 s, stainless steel 51 s, glass 203 s, plastic 405 s, wood 523 s.
(a) Sort the materials into metals and non-metals using these data, quoting values.
(b) Explain, in terms of particles, why copper’s time is a fifth of steel’s and a fiftieth of wood’s.
(c) A student says: “This proves glass is a metalloid because its time is between the metals and the plastics.” Evaluate the claim.
Reveal answer
(a) Copper (10 s) and steel (51 s) conduct heat far faster than glass (203 s), plastic (405 s) and wood (523 s); the gap between steel and glass is a factor of four, and between copper and wood a factor of fifty, so the two metals form one family and the three non-metals another.
(b) In every solid, heat passes as vibrations from atom to atom, slowly. In a metal the free electrons add a second, much faster route: they move through the whole rod carrying energy from the hot end. Copper has more free-moving electrons and a more regular lattice than steel (an iron alloy with carbon atoms disrupting it), so energy travels about five times faster; wood and plastic have no free electrons at all and rely on vibrations alone.
(c) Not supported. Glass is a compound (silicon dioxide with other oxides), not an element, so it cannot be a metalloid at all; and a single property in the middle of a range does not define a category — a metalloid is an element with a specific set of properties (brittle, semi-conducting, on the staircase). The data show only that glass is a poor thermal conductor, which every non-metal is.
Common mistakes to avoid
- Two capitals in a symbol — Co is cobalt; CO is a compound. Second letters are always small.
- “Sodium is So” — the Latin survivors: Na, K, Fe, Pb, Au, Ag, Sn, Hg, W, Cu, Sb. Learn them as a set.
- “Metals are solid, non-metals are gases” — mercury is a liquid metal; bromine a liquid non-metal; sulfur, carbon, iodine and phosphorus are solid non-metals.
- “Shiny means metal” — iodine and diamond shine; silicon shines. Use conduction, malleability and the oxide test.
- “Conducts, so it’s a metal” — graphite conducts and is a non-metal.
- Calling steel, brass or bronze elements — they are mixtures (alloys) of elements.
- Explaining conduction by saying “because it is a metal” — reach the particles: free electrons.
How we found out — 33 “simple substances”, including light
For two thousand years the elements were four: earth, air, fire and water, the theory of the Greek philosopher Empedocles, later expanded by the alchemists with mercury, sulfur and salt as “principles”. In 1661 the Anglo-Irish chemist Robert Boyle proposed a different definition in The Sceptical Chymist: an element is anything that cannot be broken into simpler substances by chemical means — a definition by experiment, not by philosophy. He could not yet say which substances passed the test. In 1789 the French chemist Antoine Lavoisier published the first list of them, 33 “simple substances”, using a balance to show that when metals burn they gain mass from the air rather than losing a “fire principle”. His list included oxygen, hydrogen, nitrogen, sulfur, phosphorus, and seventeen metals — and also light and “caloric” (heat), which he took to be substances. Lime and magnesia were on the list too; he suspected they were oxides of unknown metals, and he was right.
The unknown metals were found in 1807–08 by the Cornish chemist Humphry Davy, who passed the current from a huge battery through molten potash and watched silver beads of a new metal burst into flame at the surface: potassium, then sodium a week later, then calcium, magnesium, barium and strontium the next year — six elements in twelve months, more than anyone before or since. A method that could split a compound had shown which things were elements and which were not. Five years later Berzelius, who had spent a decade measuring the mass of every element he could get, replaced the alchemists’ pictures with letters, so that the growing list could be printed, taught and shared. By 1860, 60 elements were known — and the question had become not “what are they?” but “is there any order among them?”, the question of the next lesson.
Lavoisier listed lime (calcium oxide) as a simple substance in 1789; Davy removed it in 1808. Explain what evidence changed the classification, and why Boyle’s definition made that change possible.
Reveal answer
Nobody in 1789 had found a way to break lime into anything simpler — heating, dissolving and every reaction known left it as lime or turned it into other calcium compounds — so by Boyle’s rule it counted as an element, with Lavoisier’s note that it was probably not. Davy’s battery supplied a far stronger tool: electricity pulled the oxygen off and left a shiny metal (calcium) that burned back into lime. Lime had been split into two simpler substances, so it failed the test and was reclassified as a compound. Boyle’s definition made the change possible because it was operational — it said what to do to decide — and so it could give a different answer when a better tool arrived, without the definition itself changing. A definition by appearance or philosophy could never have been corrected by an experiment.
Where it is used now
- Botswana’s elements. The economy runs on a handful of them: carbon (diamonds at Jwaneng, Orapa and Karowe; coal at Morupule), copper and silver at Khoemacau and Motheo in the north-west, nickel and cobalt from the Selebi-Phikwe ores, gold at Mupane near Francistown, and sodium — as soda ash and salt from the brines of Sua Pan, one of the world’s largest natural soda ash operations. Every one is bought and sold by its symbol.
- Assaying. A hand-held X-ray analyser pointed at a rock face reads off the elements present in seconds, by the X-rays each element gives off when excited — Moseley’s discovery of 1913 (Lesson 4.2) as a field tool for geologists.
- Recycling and e-waste. A phone’s 70 elements are worth recovering; gold, copper, cobalt and palladium are separated by chemistry that depends on knowing exactly which family each belongs to.
- Medicine. Titanium for implants (a metal, strong, does not corrode), iodine for antiseptic and for the thyroid, lithium salts for medicine, barium sulfate for X-rays — each chosen for a property that its position on the table predicts.
- Language. In Chinese, every element has a single character; metals carry the “gold” radical 金, gases the “air” radical 气, solid non-metals the “stone” radical 石 — the metal/non-metal classification of this lesson written into the alphabet itself.
Science now — and the scientist you need to be
What is happening in 2026
The 118 elements are settled, but which of them matter is changing fast. Governments now publish lists of “critical minerals” — lithium, cobalt, nickel, copper, graphite, manganese and the rare-earth metals — because the batteries, motors and solar panels of the energy transition need them in quantities no previous century did, and Botswana’s mining strategy names copper, nickel and manganese as the next pillars after diamonds. Materials scientists have stopped asking “what is this made of?” and started asking “which of the 94 could I use instead?”: sodium in place of lithium for cheaper batteries, aluminium in place of copper in some cables, iron-based catalysts in place of platinum. In 2023 an artificial-intelligence system trained on known crystal structures proposed over two million new compounds of the known elements, hundreds of thousands of them predicted to be stable, and robotic laboratories have since made some of them. The alphabet has not grown; what people are learning to spell with it has.
The mindshift
What you need to be able to do
Three examinable skills from this lesson: write symbols correctly, including the eleven Latin ones, and read a formula symbol by symbol; classify an unfamiliar element from a list of properties, giving the reason for each property; and explain conduction and malleability at the level of free electrons. Criterion A questions in this unit routinely give you an element you have never met and ask you to place it — the mark is for the reasoning, not for recognising the name.
See an example
Coin: steel core plated with nickel — Fe and Ni, metals. Wire: Cu, metal. Pencil: C (graphite), non-metal that conducts. Spoon: Fe with Cr (stainless steel), metals. Party balloon: He, non-metal, noble gas. Battery: Zn case and C rod (a zinc–carbon cell), one metal, one non-metal. Salt: Na and Cl, a compound of a metal and a non-metal. Ring: Au, metal. Window: Si and O in silicon dioxide — a compound, not an element. Drinks can: Al, metal. The AI listed “glass, plastic, silicon and copper” — glass and plastic are compounds and mixtures, silicon and copper are the elements.
Key terms
| Element | A substance made of one kind of atom; cannot be broken into simpler substances by chemical means. 118 known, 94 natural. |
| Compound | Two or more elements chemically bonded in a fixed ratio (H₂O, NaCl, CO₂). |
| Mixture | Substances together but not bonded, separable physically (air, steel, sea water). |
| Chemical symbol | One or two letters for an element: first capital, second small. Set by Berzelius, 1813. |
| Metal | An element whose atoms share free electrons: conducts heat and electricity, malleable, ductile, shiny, usually dense and high-melting, basic oxide. |
| Non-metal | An element that is a poor conductor, brittle when solid, dull, low-melting; acidic oxide. Top right of the table. |
| Metalloid | An element on the staircase (B, Si, Ge, As, Sb, Te) with properties between the two: shiny but brittle, a semiconductor. |
| Malleable / ductile | Can be hammered into sheets / drawn into wires. |
| Basic oxide / acidic oxide | A metal oxide, which neutralises acids / a non-metal oxide, which dissolves to give an acid. |
| Free electrons | Outer electrons in a metal that move through the whole solid, carrying charge and energy. |
Think like a scientist
Criterion A Three elements, labelled P, Q and R, were tested in a laboratory. Their symbols were hidden.
| Test | P | Q | R |
|---|---|---|---|
| Appearance | Grey, shiny when cut | Yellow, dull, crumbly | Grey, shiny, glassy |
| Bulb in a circuit | Bright | Does not light | Very dim; brighter when warmed |
| Hammer | Flattens into a sheet | Powder | Shatters |
| Density / g/cm³ | 7.1 | 2.1 | 2.3 |
| Oxide + water + universal indicator | Blue (pH 10) | Red (pH 2) | Oxide does not dissolve |
| Melting point / °C | 420 | 115 | 1414 |
(a) Classify P, Q and R as metal, non-metal or metalloid, giving two pieces of evidence for each. [6]
(b) Explain, in terms of particles, why P lights the bulb brightly and Q does not. [3]
(c) Explain why P flattens under the hammer while Q turns to powder. [2]
(d) Q’s oxide turned the indicator red. Name the type of oxide and explain what the pH tells you about the element. [2]
(e) Describe where on the periodic table each of P, Q and R would be found. [3]
(f) P is zinc, Q is sulfur and R is silicon. Write the three symbols and state one use of R that depends on the result of its bulb test. [2]
Model answer
(a) P — metal: it conducts electricity well (bright bulb) and is malleable (flattens); also shiny, dense (7.1 g/cm³) and its oxide is basic (pH 10). Q — non-metal: it does not conduct (bulb off) and is brittle (powder); also dull, low density (2.1 g/cm³), low melting point (115 °C) and an acidic oxide (pH 2). R — metalloid: it is shiny like a metal but shatters like a non-metal, and conducts only slightly, more when warmed — the semiconductor behaviour that defines the family; its oxide is neither clearly basic nor acidic in water.
(b) In P the outer electrons of every atom are free to move through the whole solid — a sea of electrons around a lattice of positive ions. When the cell applies a voltage these electrons flow as a current, so the bulb lights brightly. In Q (sulfur) each electron is held in a bond between particular atoms within small S₈ molecules; there are no free electrons, so no charge can move and no current flows.
(c) In P the layers of metal ions can slide over one another when struck, and the free electrons keep the layers bonded in their new positions, so the metal changes shape without breaking — malleability. In Q the forces between the molecules are weak and the bonds do not re-form when the atoms are pushed apart, so the solid cracks along many planes and crumbles.
(d) An acidic oxide (sulfur dioxide, which dissolves in water to give sulfurous acid). A low pH from the oxide shows the element is a non-metal: metal oxides are basic and give alkaline solutions or neutralise acids, while non-metal oxides give acids.
(e) P (a metal) is to the left of the staircase line — as zinc, in the central block of transition metals. Q (a non-metal) is in the top-right triangle, to the right of the staircase — sulfur sits in Group 6, Period 3. R (a metalloid) sits on the staircase line itself, between the metals and non-metals — silicon is in Group 4, Period 3, directly below carbon.
(f) Zn, S, Si. Silicon’s slight, controllable conduction — poor when cold, better when warmed or when traces of other elements are added — makes it the material of transistors and computer chips, where a material that can be switched between conducting and not conducting is exactly what is needed.
Probe deeper — exam-style questions
Attempt every question before opening the answer. Marks in brackets show what a full answer is worth.
Define an element, and state how many elements occur naturally on Earth.
Reveal answer
A substance made of only one kind of atom, which cannot be broken down into simpler substances by chemical means [1]; 94 occur naturally (118 are known) [1].
Give the symbols for sodium, tin and tungsten, and explain why none of them begins with the first letter of its English name.
Reveal answer
Na, Sn, W [1 for all three]; Berzelius set the symbols in 1813 using the Latin names — natrium, stannum, wolfram — because Latin was the shared language of chemists across Europe [1]; the symbols were fixed then and have been kept since so that the code stays the same worldwide [1].
A student writes: “Bromine is a metal because it is shiny; carbon is a non-metal so it cannot conduct electricity; mercury is a non-metal because it is a liquid.” Identify three errors.
Reveal answer
Bromine is a non-metal — a red-brown liquid that does not conduct, is not malleable and forms an acidic oxide; shine alone does not make a metal [1]; carbon as graphite does conduct electricity, because electrons move freely between its layers, though it is a non-metal [1]; mercury is a metal — it conducts, is shiny and dense (13.5 g/cm³) — that happens to be liquid at room temperature; state is not the test [1].
Explain why copper is used for electrical wiring and why plastic is used to cover it, in terms of particles.
Reveal answer
Copper is a metal whose outer electrons are free to move through the whole wire, so they flow as a current when a voltage is applied [1]; copper is also ductile — layers of ions slide while the electrons keep them bonded — so it can be drawn into long thin wire [1]; in plastic the electrons are held in fixed bonds between particular atoms, so no current can pass through it, and it insulates the wire so the current cannot reach you [1].
True or false, with a reason: “A metal oxide dissolved in water would turn universal indicator red.”
Reveal answer
False [1]: metal oxides are basic — a soluble one such as sodium oxide gives an alkaline solution (blue/purple, high pH), and even an insoluble one neutralises acids; it is non-metal oxides, such as sulfur dioxide, that give acids and turn the indicator red [1].
An unfamiliar element sits on the staircase line of the periodic table, directly below silicon. Predict three of its properties and justify one prediction.
Reveal answer
It should be a metalloid: grey and shiny but brittle [1]; a semiconductor — conducting slightly, more when warmed [1]; with a high melting point and an oxide that is not clearly basic or acidic [1 for a third property with a reason, e.g. “because elements on the staircase share the in-between properties of silicon above it, and position on the table predicts family”]. (The element is germanium — Mendeleev’s eka-silicon, next lesson.)
Summary
- An element is one kind of atom and cannot be chemically split; 118 are known, 94 natural. Compounds are elements bonded; mixtures are not bonded.
- Symbols: one capital letter, optionally one small letter, set by Berzelius in 1813; eleven come from Latin — Na, K, Fe, Pb, Au, Ag, Sn, Hg, W, Cu, Sb.
- Metals conduct heat and electricity, are malleable, ductile, shiny, dense and high-melting and form basic oxides — all because their outer electrons are free. Non-metals are the opposite and form acidic oxides. Metalloids sit between.
- Exceptions to remember: mercury (liquid metal), graphite (conducting non-metal), iodine (shiny non-metal), bromine (liquid non-metal).
- On the table, metals lie left of the staircase line, non-metals top-right, metalloids on the line: position predicts family, and family predicts properties.
Next time → Building the table: triads, octaves, Mendeleev’s cards and the gaps that predicted gallium and germanium before anyone had seen them.