chemistry key concepts

Question 1

what is the atomic number

Answer 1

the number of protons in the nucleus of that element

Question 2

what is the number of protons always equal to

Answer 2

the number of electrons in an atom

Question 3

why is an atom neutral/ no charge

Answer 3

because the number of protons is equal to the number of electrons

Question 4

what charge do protons have

Answer 4

positive charge

Question 5

what charge to electrons have

Answer 5

negative charge

Question 6

what is the equation for atomic mass

Answer 6

number of protons + number of neutrons

Question 7

which number is the mass number

Answer 7

the bigger number

Question 8

which number is the atomic number

Answer 8

the smaller number

Question 9

what do you use to draw the electron structure

Answer 9

atomic number

Question 10

what is an isotope

Answer 10

an atom of the same element, with the same number of prons and electrons but different neutron number

Question 11

what is the relative atomic mass

Answer 11

an average of the mass number of all of the isotopes

Question 12

wha is the equation for relative atimic mass

Answer 12

(percentage abundence x atomic mass) + ( percentage abundance x atomic mass) / percemtahe abundance + percentage abundence

Question 13

what is the plum pudding model

Answer 13

a ball of positive charge with negative electrons scattered in it

Question 14

who theroised the plum pudding model

Answer 14

JJ thompson

Question 15

what did Chadwick discover

Answer 15

neutrons and what isotopes are

Question 16

when new evidinece comes up, what happens to the model

Answer 16

it changes

Question 17

what does the scatter expeiment discover

Answer 17

the nuclear model

Question 18

what happened during the scattering experiment

Answer 18

atom particles were fired at a golf leaf

Question 19

what were three observations from the scattering experiment

Answer 19

1. most of the alpjas particles went straight through the atom and meant most of the atom was empty space
2. some of the alpha particles were deflected back and it meant that the mass of the atom was concentrated in a tiny area in the centre of the nucleus
3. some of the alphas particles were deflected slightly from the particles and that meant the positive charge was not spread out but found in the nucleus

Question 20

what did bohr theorise

Answer 20

electrons are found in energy levels at specific distance

Question 21

what are three diffrences from nuclear model and the plum pudding model

Answer 21

1. in the nuclear model the positive charge is in the nucleus. whereas in the plum pudding model the atom is a ball of positive charge
2. in the nuclear model the atom is mostly empty. contrastingly, in the plum pudding model the atom has no empty
3. in the nuclear model, the mass of the atom is concentrated in the nucleus. opposingly in the plum pudding model the mass is spread out

Question 22

how is the periodic table arranged

Answer 22

in accordance with the atomic number which is the number of protons and protons weren’t discovered till later

Question 23

how many elementss were there when mendeelev organised the periodic table

Answer 23

63 elements

Question 24

how did Mendeleev arrange the elements

Answer 24

accoding to the atomic weight and their propoertires

Question 25

whike he was organising the periodic table, he concluded that some elements were undiscoverd why

Answer 25

some of the elements did not fit in the pattern and left gaps to fix the problems

Question 26

why did Mendelev swap the positions of some elements

Answer 26

for them to fit in the pattern

Question 27

what were elements put into groups based on

Answer 27

the number of electrons they have in their outershell

Question 28

what were the elements put into periods based on

Answer 28

the number of shells they have

Question 29

whagt is the same word as energy levels

Answer 29

shells

Question 30

what are the periods on the periodic tabl

Answer 30

rows

Question 31

what are the groups in the periodic table

Answer 31

collums

Question 32

what was daltons model

Answer 32

very tiny solid indivisible sphere

Question 33

what are the three subatomic particles

Answer 33

protons, electrons and neutrons

Question 34

were there any subatomic particles in the daltons model

Answer 34

no

Question 35

description of the structure of the atom

Answer 35

1. made up of prtons, neutrons and electrons 2. protons and neutrons are found in the nucleus of the atoms 3. electrons are on the shell/ energy level 4. protons are positive charge 5. electron is negative charge 6. neutrons have no charge 7. protons and neutrons have a mass of 1 8. electrons have a mass of 1/2000 ( negligible - too small, we can ignore it )

Question 36

what is relative formula mass

Answer 36

yhe sum of the relative atomic masses of all the elements shown in a chemical formula

Question 37

what is the law of conservation of mass

Answer 37

the mass of the products in a chemical reaction must be equal to the mass of the reactants

Question 38

what is concentration

Answer 38

a measure of how much of a soluble siinstamce os dissolved in a substance

Question 39

wjat is concentration measure in

Answer 39

g/dm^3

Question 40

what is the equation for concentration

Answer 40

mass/volume

Question 41

how do you convert cm^3 to dm^3

Answer 41

divide by 1000

Question 42

how do you convert dm^3 to cm^3

Answer 42

times by 1000

Question 43

what is the the size of an atom

Answer 43

1 x10^-10

Question 44

what is the size of the nucleus of an atom

Answer 44

1x10^-14

Question 45

what is avagadros number

Answer 45

the number of atoms in one mole of any substance

Question 46

what is the equation to calculate moles

Answer 46

mass/mr

Question 47

what is avogadros constant

Answer 47

6x10^23

Question 48

small -> big

Answer 48

times

Question 49

big to small

Answer 49

divide

Question 50

what is empricial formula

Answer 50

when you divide by the smallest number