2.1.1

Atomic structures and isotopes

(a) → define isotopes: as atoms of the same element with different numbers of neutrons and same number of protons

→istopes have different masses: as they have the same chemical properties but different physical properties

→ chemical properties of isotopes: the same as have the same number of electrons in outershells, which take part in chemical reactions/determining chemistry of an atom

→ physical properties of isotopes: different due to varied number of neutrons [neutral particles which only add mass to the atom] so have different physical properties due to differences in mass and density

(b) → atoms are smallest parts of an element to take place in chemical reactions

→ atomic structure: mainly empty space with a concentrated mass in the middle [nucleus] as contains heaviest subatomic particles [neutrons and protons]

→ subatomic relative charge and masses: see in diagram

→ what holds an atom together: nucleus is +ve due to protons, and -ve electrons orbit around it with their electrostatic attraction holding an atom together

→ ions: atoms that gain/lose electrons causing them to be charged; +ve has lost e-; -ve has gained e-

→ protons determine what element an atom is as all atoms/ions of the same element have the same no of it [atomic number]

Relative Mass

(c) → relative isotopic mass: mass of an isotope compared to 1/12 of carbon-12 atom [definition required]

→ relative atomic mass: weighted mean mass compared to 1/12 of carbon-12 atom [definition required]

(d) → how to find relative atomic mass using average mass of isotopes of an element: (relative abundance% x mass) + (relative abundance% x mass)etc /100

(e) → relative molecular mass: applies to simple molecules with a fixed formula/no of atoms [definition not required] → relative formula mass: applies to compounds with giant structures that use an empirical formula to represent it [definition not required]

→how to find RMM and RFM: adding up relative atomic masses of all the component atoms