U1 Periodicity

Question 1

Explain how elements in the periodic table are arranged

Answer 1

elements are arranged in horizontal rows (going across) in order of increasing atomic number and in vertical columns called Groups. elements in the same group have similar reactivity due to same number of outer electrons

Question 2

why is the periodic table arranged in this way

Answer 2

allows chemists to accurately predict physical properties and chemical behavior of any element based on its position

Question 3

covalent radius is …?

Answer 3

a measure of the size of an atom - half the distance between the nuclei of two covalently bonded atoms of an element

Question 4

describe the trends in covalent radius

Answer 4

across a period, covalent radius decreases. as atomic number increases, so does nuclear charge causing outer electrons to be more strongly attracted to the nucleus. down a group, covalent radius increases. going down a group, electron shells are added which screen the outer electrons from the nuclear charge

Question 5

what is first ionisation energy?

Answer 5

the energy required to remove one mole of electrons from one mole of gaseous atoms

Question 6

describe the trends in ionisation energy

Answer 6

across a period, ionisation energy increases. as nuclear charge increases, the outer electrons are more strongly held and more energy is required to remove them. going down a group, ionisation energy decreases. electron shells are added, which screen the outer electrons from the nuclear charge meaning they are less attracted to the nucleus and therefore require less energy to remove

Question 7

what is electronegativity?

Answer 7

electronegativity is a measure for an atom’s attraction for the electrons in a bond

Question 8

describe the trends in electronegativity

Answer 8

electronegativity increases across a period. stronger nuclear charge means the nucleus has a stronger attraction to electrons in a bond. electronegativity decreases down a group. going down a group, electron shells are added which screen bonded electrons from the nuclear charge meaning electrons are less strongly attracted to the atom

Question 9

why may the seconds ionistation energy be much higher than the first ionisation energy in an element with electron arrangement 2,8,1

Answer 9

removing the second electron involves breaking into the second shell of electrons which s closer to the nucleus. therefore more energy is required as this electron is more strongly attracted to the nucleus.