atomic structure, stoichiometry (1+2)

Question 1

element (2)

Answer 1

a substance containing only one type of atom. All the atoms in an element have the same proton number.

Question 2

atom

Answer 2

the smallest part of an element that can take part in a chemical change

Question 3

proton

Answer 3

a positively charged particle in the nucleus of the atom

Question 4

neutron (2)

Answer 4

the uncharged particle in the nucleus of an atom, with the same relative mass as a proton.

Question 5

electron

Answer 5

negatively charged particle found in orbitals outside the nucleus of an atom.

Question 6

energy levels

Answer 6

the specific distances from the nucleus corresponding to the energy of the electrons.

Question 7

What does the fact that 1. electrons are easily attracted to the anode and 2. easily deflected by an electric field tell us?

Answer 7

1. Electrons have a negative charge
2. electrons have a very small mass

Question 8

what is the mass of an electron

Answer 8

1.67*10^-27kg

Question 9

whats the charge on an electron

Answer 9

1.6*10^-19 C

Question 10

atomic number

Answer 10

the number of protons in the nucleus of an atom (A)

Question 11

isotopes

Answer 11

atoms of the same element with different mass numbers.

Question 12

Why do isotopes have similar chemical properties?

Answer 12

because they have the same number of valence electrons

Question 13

why do isotopes have different physical properties?

Answer 13

because they have different numbers of neutrons which cause small differences in mass or density

Question 14

what are the 4 uses of radioactive isotopes?

Answer 14

1. check for leaks in oil or gas pipelines
2. check thickness of paper
3. medicine- treat cancer
4. check activity of thyroid gland in throat

Question 15

electronic configuration

Answer 15

a way of representing the arrangement of the electrons in atoms

Question 16

first ionization energy

Answer 16

the energy required to remove 1 mole of electrons from 1 mole of atoms of an element in the gaseous state to form one mole of gaseous ions.

Question 17

what are the key points when writing equations for successive ionization energies?

Answer 17

1. atoms and ions are in the gaseous states
2. The charge on the ion on the right hand side gives the number of the IE

Question 18

what do big differences between some successive IEs indicate ?

Answer 18

These large changes indicate that for the second of these 2 IE’s, the electron is being removed from a principal quantum shell closer to the nucleus

Question 18

why do successive IEs increase across a period?

Answer 18

the successive IE increases, because the net positive charge on the ion gets greater as each electron is removed, there is a greater attractive force between protons and electrons, hence more energy is needed to overcome these attractive forces.

Question 19

how does the size of the nuclear charge influence IE?

Answer 19

in general, IE increases as proton number/ nuclear charge increases

Question 20

how does distance of outer electrons from the nucleus influence IE?

Answer 20

In general the further the outer electron shell is from the nucleus, the lower the IE.

Question 21

how does the shielding effect influence the IE?

Answer 21

In general, the IE is lower as the number of full electron shells between the outer electrons and the nucleus increases.

Question 22

what is the shielding effect

Answer 22

the ability of inner shell electrons to reduce the effect of the nuclear charge on outer shell electrons.

Question 23

subsidiary quantum shells

Answer 23

regions of the principal quantum shells where electrons exist in defined areas associated with particular amounts of energy.

Question 24

atomic orbitals

Answer 24

regions of space outside the nucleus that can be occupied by a max of 2 electrons.

Question 25

spin pair repulsion

Answer 25

pairing the spinning electrons so they spin in opposite directions reducing the repulsion.

Question 26

free radical

Answer 26

a species with one or more unpaired electrons.

Question 27

atomic radius

Answer 27

half the distance between the nuclei of 2 covalently bonded atoms of the same type.

Question 28

trend in atomic radius

Answer 28

atomic radius increases down any group atomic radius decreases across any period

Question 29

trend in ionic radius

Answer 29

ionic radius increases down any group ionic radius decreases across any period

Question 30

general trend in IE across a period and why

Answer 30

IE increases across a period because - 1. nuclear charge increases 2. distance between nucleus and outer shell remains constant 3. shielding remains constant

Question 31

why is there a rapid decrease in IE between the last element in one period and the first element in the next period?

Answer 31

because- 1. the distance (nucleus and outer shell) increases 2. shielding increases 3. these 2 factors cancel out increase in nuclear charge

Question 32

relative isotopic mass

Answer 32

the mass of a particular atom of an isotope compared to the value of the unified atomic mass unit

Question 33

relative formula mass

Answer 33

the weighted average mass of one formula unit compared to the value of the unified atomic mass unit.

Question 34

relative atomic mass

Answer 34

the weighted average mass of atoms in a given sample of an element compared to the value of the unified atomic mass unit

Question 35

water of crystallization

Answer 35

a specific number of moles of water associated with a crystal structure

Question 36

hydrated compound

Answer 36

compound which contains a definite number of moles of water in their structure

Question 37

anhydrous compound

Answer 37

compound containing no water of crystallization

Question 38

use of mass spectrometry

Answer 38

measure the mass of each isotope present in an element

Question 39

calculation of Ar from mass spectra

Answer 39

Ar= (isotopic mass * percentage abundance) / 100

Question 40

calculation of no. of carbon atoms

Answer 40

n= 1.1*abundance of M+1 / 100*abundance of M

Question 41

how to identify bromine presence in an organic compound

Answer 41

If the peak heights are equal, there is one atom of bromine per molecule

Question 42

how to identify chlorine presence in an organic compound

Answer 42

if the peak heights are in the ratio 3(M) to 1(M+2) there is one atom of chlorine per molecule

Question 43

mole

Answer 43

the amount of substance which contains 6.023*10^23 specified particles.

Question 44

unified atomic mass unit

Answer 44

one twelfth of the mass of a carbon-12 atom