chemistry ionic and covalent bonding

3

covalent bonding:

• when non metal atoms share electron pairs to obtain a full outer shell

whats a molecule?

2 or more atoms covalently bonded

can only contain non - metals

explain covalent bonding:

• when atoms are CLOSE, the ATTRACTIONS between the ELECTRON and the NUCLEUS are so strong, so a MOLECULE of HYDROGEN (H2) is formed

• the atoms are held together by the ATTRACTIONS between the 2 NULEI and two SHARED PAIR OF ELECTRONS

• when non metal atoms REACT, they both need to GAIN ELECTRONS to FILL their OUTER SHELL and become STABLE

ionic bonds:

• metals react with non - metals to form salts

• they become ions because of the loss and gain of an electron

• they both become stable because they have a full outer shell

what happens when salts are formed:

an electron is LOST from the outer shell of the METAL atom

electrons are GAINED by the NON METAL atom

sodium ion:

NA +

• overall positive charge

• looses an electron

• to achieve a full outer shell

chlorine ion:

CL -

• overall negative

• goes from 7 → 8 electrons in its outer shell

• becomes stable because of the gain of an electron

• full outer shell

is the mass of an ion the same or different to the mass of an atom?

SAME

• electrons weigh almost nothing

• but the mass of an ion includes the mass of the protons and neutrons, which remain unchanged from the atom

if an atom loses two electrons to form an ion what charge will it have

2+

• electrons have a negative charge

describe the ionic bonds between a metal and a non metal atom (in terms of electron transfer)

• the metal atom looses electrons to form a positively charged ion

• the non metal gains these electrons to form a negatively charged ion

• these oppositely charged ions are strongly attracted to each other by electrostatic forces

• these form an ionic bond