C1.1:The Fundamental Ideas

ATOM - A neutral particle made up of protons and neutrons in the nucleus, with electrons surrounding the nucleus

The nucleus is the middle part of the atom containing protons and neutrons. Electron shells surround the nucleus and contains electrons.

PROTON - POSITIVE = +1

NEUTRON - NEUTRAL = 0

ELECTRON - NEGATIVE = -1 

Atoms have no overall charge, they are neutral. The charge on the electrons (-1) cancels out the charge on the protons (+1) meaning the number of protons always equals the number of electrons in an atom.

ELEMENT - A substance that is made up of only one type of atom

Different elements have atoms with different numbers of protons.

The periodic table is a table that contains all the known elements. Elements are represented by symbols (e.g. Oxygen - O, Sodium - Na)

All elements with similar propertis are in groups (vertical columns).

All elements with the same amount of electron shells are in periods (horizontal rows).

Metals are located on the left-hand side of the table.

Non-metals are located on the right-hand side of the table.

Each symbol in the periodic table has two numbers by it. The larger (top) number is the mass number and the smaller (bottom) number is the atomic number.

ATOMIC NUMBER (proton number) - Number of protons in an atom

MASS NUMBER - Total number of protons and neutrons in an atom

The number of electrons is equal to the number of protons.

Elements in a group have the same number of electrons in their outer shell giving them similar chemical and physical properties.

e.g. Alkali metals/group 1 elements (Li, Na, K, Rb, Cs, Fr) have 1 electron in their outer shell. They react with water to form an alkaline solution and hydrogen gas and also react with oxygen to form an oxide.

e.g. Halogens/group 7 elements (F, Cl, Br, I, At) all have 7 electrons in their outer shell. They have low melting and boiling points which increase as you go down the group. They react with metals to form metal halides.

e.g. Noble gases/group 0 elements (He, Ne, Ar, Kr, Xe, Rn) have 8 electrons in their outer shell (apart from helium which has two). They have a stable arrangement of electrons as the outer shell is full making them unreactive.

e.g. Transition metals (Fe, Co, Ni, Cu, Zn, Au...) are good conductors of heat and electricity, have high melting points and high densities and can be hammered or bent into shape easily.

ELECTRON SHELLS (energy levels) - A region of an atom that contains electrons

The electron shells with the lowest energy are always filled first - these are the ones closest to the nucleus. Only a certain number of electrons are allowed in each shell:

1st shell - 2

2nd shell - 8

3rd shell - 8

How to draw the electronic structure of an element?

• Find the number of electrons in an atom of the element using the periodic table
• Draw the first electron shell and add 2 electrons to it
• Draw the second electron shell and add 8 electrons to it
• Draw the third electron shell, if needed and add 8 electrons to it

Atoms form chemical bonds with other atoms to form compounds. Making bonds involves atoms giving away, taking or sharing electron. If the different atoms aren't bonded together then it forms a mixture.

COMPOUND - A substance made up of two or more elements that are chemically joined together

Compounds can be small molecules or great big structures (lattices).

They are formed from a metal and non-metal which consists of ions. Ions are charged particles.

They are made when atoms lose or gain electrons.

Positive ions are formed when metal atoms lose electrons.

Negative ions are formed when non-metal atoms gain electrons.

Word and symbol equations are used to show the reactants (substances that react together) and products (substances that are made in a reaction) of a chemical reaction.

Conservation of Mass - The mass of reactants is equal to the mass of products, because no atoms are gained or lost during a chemical reaction.

A symbol equation gives you information about the number of atoms of each element involved in a reaction.

e.g. Magnesium + Oxygen > Magnesium Oxide

       2Mg + O2 > 2MgO