Periodicity

Question 1

whats a period

where does period 1 start

are there trends in periods

Answer 1

the horizontal rows of elements

at hydrogen and helium

yes

Question 2

whats a group

whats special about the electrons

Answer 2

a vertical column in the periodic table

all elements have the same number of electrons in the outermost principle energy level and have similar properties

Question 3

what are the elements called that lie on the metal-nonmetal dividing line called

what properties do they have

Answer 3

metalloids

a combination of metallic and nonmetallic properties

Question 4

what are the names of the different blocks in periodic table

why are they called that

Answer 4

s p d f

the block of an element corresponds to the sublevel where the outermost (highest energy) is found

Question 5

what’s metallic bonding

Answer 5

strong electrostatic forces of attraction between positive metal ions and delocalised electrons

this forms a giant metallic lattice which strong metallic bonds extend throughout

Question 6

what’s covalent bonding

where are 2 versions of covalent bonding found

Answer 6

shared pair of electrons between two or more non metals

giant covalent structures and simple molecular structures

Question 7

what 3 things does strength of metallic bonding depend on

Answer 7

1) charge on positive ion
2) number of delocalised electrons
3) size of ion

Question 8

what 2 things affect size of van der waaal forces between molecules

Answer 8

1) mr
2) surface area contact

Question 9

explain trend in melting and boiling point of the simple molecular substances in peirod 3

Answer 9

van der waal forces increase with size of molecule

sulfur forms S8 molecule
phosphorus forms P4 molecule
Ar is a single atom

Question 10

what happens to atomic radius across a period and why

Answer 10

decreases

number of protons increases

shielding is constant

electrons more strongly attracted to the nucleus and so draws them closer to the nucleus

Question 11

what happens to atomic radius down a group and why

Answer 11

increases

number of principal energy levels increases

more shielding

electrons less attracted to nucleus

Question 12

how to work out atomic radius

Answer 12

look at pair of identical atoms which form a bond and measure the middle of them

Question 13

first ionisation energy definition

Answer 13

minimum amount of energy needed to remove one electron from a gaseous atom to form a 1+ ion which is also gaseous

Question 14

definition of periodicity

Answer 14

repeating trends of physical and chemical properties with increasing atomic number