Topic 1-Fundementals of chemistry

1. Topic 1-Fundementals of chemistry Useful links to click on- all hyperlinked BBC Bitesize link http://www.my-gcsescience.com/core/ Go to C1 and revsie videos on- Atoms, periodic table, chemical reactions

2. C1 1.1 ATOMS, ELEMENTS & COMPOUNDS • All substances are made of atoms • Elements are made of only one type of atom • Compounds contain more than one type of atom • Compounds are held together by bonds An atom is made up of a tiny nucleus with electrons around it • Each element has its own symbol in the periodic table • Columns are called GROUPS. • Elements in a group have similar properties • Rows are called PERIODS • The red staircase splits metals from non-metals

3. C1 1.2 ATOMIC STRUCTURE • Atoms contain PROTONS, NEUTRONS & ELECTRONS • Protons and Neutrons are found in the NUCLEUS • Electrons orbit the nucleus Any atom contains equal numbers of protons and electrons • ATOMIC NUMBER the number of protons in the nucleus  the periodic table is arranged in this order • MASS NUMBER the number of protons plus neutrons Number of neutrons = Mass Number – Atomic Number

4. C1 1.3 ELECTRON ARRANGEMENT • Electrons are arranged around the nucleus in SHELLS (or energy levels) • The shell closest to the nucleus has the lowest energy • Electrons occupy the lowest available energy level High energy shell This is how we draw atoms and their electrons Low energy shell Sodium • Atoms with the same number of electrons in the outer shell belong to the same GROUP in the periodic table • Number of outer electrons determine the way an element reacts • Atoms of the last group (noble gases) have stable arrangements and are unreactive

5. C1 1.4 FORMING BONDS • Atoms can react to form compounds in a number of ways: • Transferring electrons  IONIC BONDING • Sharing electrons  COVALENT BONDING • IONIC BONDING • When a metal and non-metal react • Metals form positive ions • Non-metals from negative ions • Opposite charges attract • A giant lattice is formed • COVALENT BONDING • When 2 non-metals bond • Outermost electrons are shared • A pair of shared electrons forms a bond • CHEMICAL FORMULAE • Tells us the ratio of each element in the compound • In ionic compounds the charges must cancel out: • E.g. MgCl2 • We have 2 chloride ions for every magnesium ion

6. C1 1.5 CHEMICAL EQUATIONS • Chemical equations show the reactants (what we start with) and the products (what we end up with) • We often use symbol equations to make life easier CaCO3 CaO + CO2 • This is balanced – same number of each type of atom on both sides of the equation • We can check this by counting the number of each type on either side Ca = 1 C = 1 O = 3 Ca = 1 C = 1 O = 3 MAKING EQUATIONS BALANCEEquations MUST balance We can ONLY add BIG numbers to the front of a substance We can tell elements within a compound by BIG letters CaCO3 this is a compound made of 3 elements (calcium, carbon and oxygen) H2 + O2 H2O Add a 2 to the products side to make the oxygen balance H2 + O2 2H2O This has changed the number of hydrogen atoms so we must now adjust the reactant side: 2H2 + O2 2H2O H = 2 O = 2 H = 2 O = 1 H = 2 O = 2 H = 4 O = 2

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