C1 - Air and Water

• An atom is made of protons and neutrons as the nucleus and electrons orbitting the nucleus in the outer shells
• Atoms are neutral because they have equal numbers of positive and negative charges.
• Ions are atoms that have lost or gained electrons, so their charge isn't balanced anymore.
• The number of protons determines the atomic number
• Isotopes are atoms with different masses but same atomic number
• Ions are charged particles formed when an electron is lost or gained by an atom, resulting in either positively or negatively charged ions
• Protons have a positive charge (+1)
• Neutrons have no charge (0)
• Electrons have a negative charge (-1)
• Atoms can gain or lose electrons to form ions
• Group 0/8 are called the 'Noble Gases' and consist of helium, neon, argon, krypton, xenon and radon. As you go down the group, the boiling/melting points and density increase. They are all also monatomic meaning they travel as single atoms. They also have a very low reactivity due to them all having a full shell so are stable.
• Group 1 is called the 'Alkali Metals' and consist of lithium, sodium, potassium, rubidium and francium. They all have simlar properties - low melting/boiling points, low density and very soft. They all form ionic compounds due to how easily they loose 1 electron but don't form covalent bonds. Since they can easily loose their electron, it means they are highly reactive and as you go down in the group, they become more and more reactive. For example, if you put them in water, they react vigorously to produce hydrogen gas and a hydroxide of the metal.
• Group 7 is called the 'Halogens' and consists of flourine, chlorine, bromine, iodine and astatine. They exist as diatomic molecules meaning they travel in pairs and share one pair of electrons making a covalent bond and giving both atoms a full outer shell. As you go down the group, the melting/boiling points increase but the reactivity decreases as you go down as it gets harder to attract the extra electron to make a full shell due to the shell being furthur away from the nucleus (the atomic radius is larger). When reacting with an alkali metal, it creates a salt via a displacement reaction.
• John Dalton - discovered neutrons which are in a sphere
• JJ Thompson - discovered the electron, discovered the plum pudding model of the atom
• Rutherford - alpha particles were emitted from the centre of the nucleus.
• Ernest Rutherford - discovered protons and alpha particles, created the nuclear model of the atom where there was a small positively charged nucleus surrounded by negatively charged electrons.
• Niels Bohr - proposed that electrons orbit the nucleus in shells.
• Isotopes - Atoms of the same element that contain the same amount of protons but differing amounts of neutrons. Isotopes have the same chemical properties because they have the same number of protons. However, they do not have the same physical properties such as mass.