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2.1Chapter 2: Elements, Compounds and Mixtures

Elements and the periodic table — Alhussan Chemistry - Stage 7 Revision Notes & Topical Questions

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📚 Alhussan Chemistry - Stage 7 Hub / Topical Revision
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Lesson summary

2.1 Elements and the periodic table — Alhussan International Academy — Chemistry (Stages 7–9) notes: Define an element and use the layout of the periodic table to find information about elements and predict their properties.Element = a pure substance made of only one type of atom…

  • Everything
  • Names and symbols
  • State at room temperature
  • Carbon, hydrogen, oxygen and nitrogen
  • Stepped line
  • Named groups

Part 1 of 7What an element is

What an element is
Element
Element a pure substance made of only one type of atom, which cannot be split into other substances.
  • Each element has its own type of particle and its own properties.
  • Oxygen, iron, carbon and gold are elements.
Everything
  • Everything every material on Earth, and everything in the Universe, is made from the particles of one or more elements.
Number
  • Number there are 118 known elements, about 90 of them natural and the rest made in laboratories.
Names and symbols
  • Names and symbols each has its own name and a one- or two-letter symbol, such as O, Fe, C and Au.
State at room temperature
  • State at room temperature most are solids, a few such as hydrogen, oxygen and nitrogen are gases, and only mercury and bromine are liquids.

Part 2 of 7Substances and materials

Materials
  • Materials there are millions of materials and most are mixtures.
Substance
  • Substance a material with just one type of particle.
Elements are the special substances that cannot be split into other substances.

Part 3 of 7Uses depend on properties

Platinum
  • Platinum it is expensive, with 1 kg costing more than 33 000 US dollars in 2020, because its properties give it important uses.
  • Surgeons insert platinum stents into narrowed blood vessels to keep them open.
  • Catalytic converters in cars contain platinum to turn harmful exhaust gases into less harmful ones.
  • Hard drives that store computer data contain platinum.
  • South Americans made platinum and gold jewellery about 2000 years ago.
Iron
  • Iron many useful metal objects contain iron.

Part 4 of 7Common elements

1Hydrogen
  • Hydrogen the most common element in the Universe, a non-metal.
2Helium
  • Helium the second most common element in the Universe.
3Carbon, hydrogen, oxygen and nitrogen
  • Carbon, hydrogen, oxygen and nitrogen living things are mainly made of these, and all living things including you are mainly carbon.
4Nitrogen
  • Nitrogen the most common element in the Earth's atmosphere.

Part 5 of 7How the table is organised

1
Periodic table
Periodic table a table that lists all the elements in order of increasing atomic number and groups together elements with similar properties.
2
Periods
  • Periods the rows.
3
Groups
  • Groups the columns, and elements in the same group have similar properties because their atoms have the same number of outer electrons.
4
Stepped line
  • Stepped line it splits the elements into metals on the left and non-metals on the right.
  • Properties of metals and non-metals are studied in Chapter 3.
5
Named groups
  • Group 1 is the alkali metals, Group 7 the halogens and Group 0 the noble gases.
6
Transition metals
  • Transition metals the block in the middle contains iron, copper and zinc.
7
Hydrogen
  • Hydrogen it sits at the top on its own because it has unique properties and is a non-metal.

Part 6 of 7Information from the table

  • Each box shows the symbol, name, atomic number and often the relative atomic mass.
    • Sodium shows Na, atomic number 11 and relative atomic mass 23.
    • The atomic number is the number of protons.
RegionTypical properties
MetalsShiny, conduct electricity and heat, malleable, usually solid
Non-metalsDull when solid, poor conductors, brittle if solid
Noble gasesUnreactive gases

Part 7 of 7Patterns you can predict

Patterns you can predict
Across a period
  • Across a period elements change gradually from metals to non-metals.
  • Silicon lies close to the dividing line, has properties of both and is a semiconductor used in computer chips.
Down Group 1
  • Down Group 1 the metals become softer and more reactive, so potassium is more reactive than lithium and rubidium reacts violently with water.
Down Group 7
  • Down Group 7 the halogens become darker in colour and less reactive.
Prediction
  • Prediction find the group of an unfamiliar element and use the pattern of its neighbours.
Sodium
  • Sodium it is in Group 1, so it is a soft, reactive metal that reacts with water.

Key terms

TermMeaning
ElementA substance made of one type of atom that cannot be split into simpler substances.
Periodic tableA table of the elements in order of atomic number grouped by properties.
GroupA column of the periodic table.
PeriodA row of the periodic table.
Atomic numberThe number of protons in an atom.
SubstanceA material with only one type of particle.

Avoid these mistakes

1
Confusing periods (rows) with groups (columns).
2
Thinking hydrogen is a metal because it is on the left.
3
Saying an element can be broken down by a chemical reaction.
4
Believing all elements are solids at room temperature.

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