Topic 1 Key Concepts In Chemistry

Question 1

What is the charge of these
Electron
Proton
Neutron

Answer 1

Electron negative
Proton positive
Neutron neutral/no charge

Question 2

What 2 subatomic particles are in the nucleus

Answer 2

Protons and neutrons

Question 3

What subatomic particle exists in shells around the atom

Answer 3

Electrons

Question 4

Where is most of the mass in an atom

Answer 4

In the nucleus
The nucleus is very small compared to the whole atom

Question 5

Why do atoms have same number of protons and electrons

Answer 5

This is so the charges balance out and there is no overall charge of the atom
If it had a charge it would be an ion

Question 6

What does the mass number of an atom mean

Answer 6

Number of protons and neutrons in an atom

Question 7

How did john dalton model describe atoms

Answer 7

He thought they were solid spheres

Question 8

What model did JJ Thompson suggest about model of an atom

Answer 8

Suggested the plum pudding model
A sphere of mainly positive charge that contained smaller negative charges scattered around

Question 9

What did Ernest Rutherford a experiment of firing positively charged alpha particles into a nucleus suggest (with GEIGER AND MARSDEN)

Answer 9

That most of atom was empty space
At centre of atom there was a small positive charge and the rest of the atom was surrounded by negative charges

Question 10

What did Bohr model that is used nowadays suggest about the electrons in an atom

Answer 10

That the electrons were in fixed positions in electron shells around the atom and not just scattered

Question 11

how are isotopes different from normal elements

Answer 11

different mass number
same atomic number

same amount proton electron
different amount neutrons

Question 12

how to work out relative atomic mass from isotopic abundances

Answer 12

x each relative atomic mass by its relative abundance then add em up

divide by sum of the isotopic abundances

Question 13

exam q- copper has two stable isotopes copper 63 and copper65
cu63 has abundance of 69.2
cu has abundance of 30.8
calculate relative atomic mass of copper

Answer 13

(63x69.2) + (65x 30.8) = 6361.6

6361/100= 63.6

1. isotopic mass x abundance
2. add them up
   3didvide by sum of isotoptic abundances

Question 13

explain what Dmitri Mendeleev done with periodic table

Answer 13

1. sort element into groups based on properties
   2 put em in order of atomic mass
   3,.similar properties in columns
2. some end up in wrong column so switched the order
   5.predicted properties of discovered elements

Question 14

how are ionic bonds attracted

Answer 14

strongly attracted by electrostatic forces

Question 15

what will a metal and non metal form in ionic bonding (charge)

Answer 15

metal cation
non metal anion

Question 16

structure of ionic compound

Answer 16

regular lattice structure
closely packed
electrostatic forces of attraction between oppositely charged ions

Question 17

what kinda melting nd boiling point do ionic compounds have nd why

Answer 17

high mp
high bp
lots of energy to overcome electrostatic forces of attraction

Question 18

ionic compounds conducting electricity

Answer 18

when solid cant conduct ions held in place

liquid nd gas ions free to move = can conduct

dissolved in water ions separate so free to move

Question 19

different models for structures

pros nd cons

Answer 19

2d
+what atom something contain
+how atom connected
-no shape
-no size

dot nd cross
+how compounds formed
+where electrons came from
-no size
-no show how arranged

3d
+arrangement
-only show outer layer

ball nd stick
+ help visulise
+more realistic
-no show different sizes of atom

Question 20

ionic bonding defi

Answer 20

the transfer of electrons between metal and non metal

Question 21

covalent bonding defi

Answer 21

the sharing of electrons between 2 non metals

Question 22

strength of covalent compounds

Answer 22

strong covalent bonds
weak intermolecular forces
overall weak

Question 23

why mp nd bp for covalent substances low

Answer 23

only needa break intermolecular forces
they weak
so mp nd bp low
no require lots energy

Question 24

can covalent substances conduct elect

Answer 24

no
arent charged
no free electrons

Question 25

diamond

Answer 25

tetrahedral structure
4 covalent bond
strong covalent bonds so high mp nd bp
rigid lattice structure- hard- cutting tools
cant conduct electricity no free electrons

Question 26

graphite

Answer 26

3 covalent bonds- 1 fee ion so can conduct elec
high mp nd bp- covalent bonds in layers
free to move over eachother- lubricant

Question 27

how do u find relative formula mass (Mr)

Answer 27

Ar all added together

all big numbers added together

Question 28

how to find percentage mass of compound

Answer 28

Ar of what element we looking for x how many of that element there are / Mr of whole compound

Question 29

What is the percentage mass of carbon (C) in methane (CH4)?

(Ar of carbon = 12, Ar of hydrogen = 1)

Answer 29

1x 12 / 16 x100

1- find ar of element we lookin for (c)
2- find how many of that element there are (1)
3- times them
4-divide by sum of the mr of that comound

Question 30

what is a mole

Answer 30

the unit we use for chemical we have

Question 31

what is 1 mole equal to

Answer 31

6.02x10 to the power of 23 particles= the ar of compound

carbon- ar =12g=1mole

Question 32

moles formula

Answer 32

mass/mr

rearrange
mass=molesx mr

Question 33

exam q find the mass of carbon in 3 mol of co2

Answer 33

mass= molesxmr

3=moles

mr of carbon=12

3x12=36g of co2

Question 34

‘Calculate the mass of sodium oxide (Na2O) that can be made by completely burning 5.0g of sodium (Na) in oxygen.

Answer 34

1- balance the equation 4Na+ o2 –> 2Na2 O
sodium=known
sodium oxide=unknown

2-calculate mole of known substance
mole=mass/mr
5/23=0.217

3 find mole of unknown substance using ratios
4:2=2:1
0.217/2=0.1085

4-find mass of unknown (using mole we just found)
mass=molexmr
62x0.1085=6.73g

Question 35

concentration (g/dm cubed)

Answer 35

mass/volume

hint- look at the units

Question 36

concentration(mol/dm cubed)

Answer 36

amount of substance/volume

Question 37

volume of gas

Answer 37

moles x 24

Question 38

mole