3.1 the periodic table

what is periodicity?

• repeated trend in properties across a period

what is the trend across a period?

• the s- and p- sub shells are filled in the same way

what is the trend down a group?

• elements in each group have atoms with same number of electrons in outermost shell

• same number of electrons in each sub shell

what is ionisation energy?

• measures how early an atom loses electrons to form positive ions

what is the process of ionisation which occurs in a mass spectrometer?

1. elements are first vaporised to form a gas

2. elements are then ionised by losing 1 electron

what is the definition of the first ionisation energy of an element?

• energy required to remove 1 electron from each atom in 1 mole of gaseous atom of an element to form 1 mole of gaseous 1+ ions

what is the definition of the second ionisation energy of an element?

• energy required to remove 1 electron from 1 mole of Li⁺ ions to form one mole of Li²⁺

what is the definition of the third ionisation energy of an element?

• energy required to remove 1 electron from 1 mole of Li²⁺ ions to form one mole of Li³⁺

what are the factors affecting ionisation energy size?

1. atomic radius

2. nuclear charge

3. electron shielding

how does atomic radius affect ionisation energy?

• larger the atomic radius, the smaller electrostatic forces of attraction between the nucleus and the outer electron

• this is because the positively charged nucleus is further from the outermost electrons

• lower ionisation energy as less energy is required to remove an electron from outer shell

how does nuclear charge affect ionisation energy?

• higher the nuclear charge, the larger the electrostatic forces of attraction between the outer electrons and the nucleus

• more energy will be required to remove the outer electron resulting in a higher ionisation energy

how does electron shielding affect ionisation energy?

• inner electron shell shield the positive charge of the nucleus from the outermost electrons

• the larger the atom, more electron shells, so greater shielding

• this reduces the size of ionisation energy

how many ionisation energies can an element have?

• same number of electrons

what does it mean if there is a large increase between different ionisation energies?

• electron must be removed from a different shell

• this electron has less shielding an is closer to the nucleus so needs more energy to remove

what predictions does successive ionisation energy allow us to make?

• the number of electrons in the outer shell

• the group of the element in the periodic table

• the identity of the element