atomic structure p1

Question 1

explain the current model of the atom

Answer 1

• protons and neutrons are found in the nucleus
• electrons orbit the nucleus in shells
• the nucleus is tiny compared to the total volume of atom
• most of atom’s mass is in the nucleus
• most of the atom is empty space between the nucleus and the electrons

Question 2

what is the charge of a proton and an electron?

Answer 2

proton = +1
electron = -1

Question 3

which particle has the same mass as proton?

Answer 3

neutron

Question 4

which two particles make up most of atom’s mass?

Answer 4

protons and neutrons

Question 5

what does the atomic number show about an element?

Answer 5

atomic number = number of protons in an atom

Question 6

how is the mass number calculated?

Answer 6

mass number = number of protons + number of neutrons

Question 7

isotope

Answer 7

atoms of the same element with different number of neutrons and therefore different mass number

Question 8

why do different isotopes of the same element react in the same way?

Answer 8

• neutrons have no impact on the chemical reactivity
• reactions involve electrons, isotopes have the same number of electrons in the same arrangement

Question 9

relative atomic mass

Answer 9

weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon-12

Question 10

relative isotopic mass

Answer 10

the mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12

Question 11

the relative isotopic mass is same as which number?

Answer 11

mass number

Question 12

what two assumptions are made when calculating mass number?

Answer 12

• contribution of the electron is neglected
• mass of both proton and neutron is taken as 1.0

Question 13

how to calculate the relative molecular mass and relative formula mass?

Answer 13

both can be calculated by adding the relative atomic masses of each of the atom making up the molecule or the formula

Question 14

what are the uses of mass spectrometry?

Answer 14

• identify unknown compounds
• find relative abundance of each isotope of an element
• determine structural information

Question 15

what is the m/z value of the M+ ion from a graph??

Answer 15

last peak

Question 16

what does the principal quantum number indicate?

Answer 16

the shell occupied by the electrons

Question 17

what is a shell?

Answer 17

a group of orbitals with the same principal quantum number

Question 18

how many electrons can each shell hold?

Answer 18

1st - 2
2nd - 8
3rd - 18
4th - 32

Question 19

what is an orbital?

Answer 19

a region around the nucleus that can hold up to two electrons with opposite spin
95% (?) chance of finding an electron

Question 20

what are the four types of orbitals?

Answer 20

s, p, d, f

Question 21

what shape are the orbitals?

Answer 21

s - spherical
p - dumb bell

Question 22

how many orbitals are present in each sub shell?

Answer 22

s - 1, 2 electrons
p - 3, 6 electrons
d - 5, 10 electrons
f - 7, 14 electrons

Question 23

what rules are electrons arranged in a shell by?

Answer 23

• electrons are added one at a time
• lowest available energy level is filled first
• each energy level must be filled before the next one can fill
• each orbital is filled singly before pairing
• 4s is filled before 3d

Question 24

why does 4s orbital fill before 3d orbital?

Answer 24

4s has a lower energy than 3d before it is filled

Question 25

how can the electron configuration be written in short?

Answer 25

the noble gas before the element used to abbreviate (often [Ar])

Question 26

how are the elements arranged in a periodic table?

Answer 26

they are arranged in the order of increasing atomic numbers

Question 27

what is a period on a periodic table?

Answer 27

horizontal rows

Question 28

what is a group on a periodic table?

Answer 28

vertical columns

Question 29

how is the group number related to the number of electrons?

Answer 29

group number = number of electrons in outer shell

Question 30

what is meant by periodicity?

Answer 30

the repeating trends in chemical and physical properties

Question 31

first ionisation energy

Answer 31

the energy required to remove a mole of electrons from a mole of gaseous atoms to form one mole of gaseous 1+ ion under standard conditions

Question 32

first ionisation energy equation of Mg

Answer 32

Mg(g) --> Mg+(g) + e-

Question 33

what are the factors that affect ionisation energy?

Answer 33

- atomic radius - nuclear charge - electron shielding or screening

Question 34

why does ionisation energy increase across a period?

Answer 34

increased nuclear charge, decreased atomic radius, same electron shielding more energy needed to remove first electron

Question 35

why does first ionisation energy decrease between group 2 to 3?

Answer 35

decreases between 2 to 3 because in group 3 the outermost electrons are in p orbitals whereas in group 2 they are in the s orbital so the electrons are easier to remove from p as it is further from the nucleus

Question 36

why does first ionisation energy decrease between groups 5 and 6?

Answer 36

decrease due to the group 5 electrons in p orbital which are single electrons in group 6 the outermost electrons are spin paired, with some repulsion therefore the electrons are slightly easier to remove

Question 37

does first ionisation increase or decrease between the end of one period and the start of the next? why?

Answer 37

decrease there is increase in atomic radius increase in electron shielding

Question 38

does first ionisation increase or decrease down a group? why?

Answer 38

decrease shielding increases, atomic radius increases, nuclear charge increases however outweighed by radius and shielding

Question 39

describe the structure, forces and bonding in every element across period 2? (Li, Be, B, C, N, O, F, Ne)

Answer 39

Li & Be --> giant metallic; strong attraction between positive ions and delocalised electrons; metallic bonding B & C --> giant covalent; strong forces between atoms; covalent N2, O2, F2, Ne --> simple molecular; weak intermolecular forces between molecules; covalent bonding within molecules and intermolecular forces between molecules

Question 40

describe the structure, forces and bonding in every element across period 3: Na, Mg, Al, Si, P, S, Cl, Ar

Answer 40

Na, Mg, Al --> giant metallic; strong attraction between positive ions and delocalised electrons; metallic bonding Si --> giant covalent; strong forces between atoms; covalent P4, S8, Cl2, Ar --> simple molecular; weak intermolecular forces between molecules and intermolecular forces between molecules

Question 41

what are the 4 stages of mass spec?

Answer 41

1 - ionisation - element is vaporised and injected into the mass spec where a high voltage is passed over the chamber causing electrons to be removed leaving +1 charged ions 2 - acceleration 3 - ion drift - ions deflected by a magnetic field into a curved path 4 - detection - positive ions hit negatively charged detection plate, gaining an electron and producing a flow of charge - the greater the abundance the greater the current produced 5 - analysis