C1.2 Atomic Structure

Question 1

What are atoms?

Answer 1

The smallest particles of an element that still have its chemical properties.

Question 2

What are different elements made from?

Answer 2

Diff. atoms.

Question 3

What is a molecule?

Answer 3

Made from 2 or more atoms joined together by attractive forces called chemical bonds.

Question 4

What are chemical bonds?

Answer 4

Attractive forces (that join 2 or > atoms in a molecule).

Question 5

What can the atoms in a molecule be?

Answer 5

1) same (e.g. O2 molecule made from 2 O atoms)
2) diff. (e.g. CO2 molecule made from C atom & 2 O atoms)

Question 6

What is the size of an atom given by?

Answer 6

Its atomic radius, which is 1/2 its diameter.

Question 7

What is bond length?

Answer 7

The distance between the centres of joined atoms.

Question 8

What are atomic radii typically around?

Answer 8

10^-10m.

Question 9

What are bond lengths typically around?

Answer 9

10^-10m (same as atomic radii, which gives the size of an atom).

Question 10

What must you remember about molecules?

Answer 10

They have diff. chem. & physical properties from the atoms they contain.

Question 11

What is inside an atom?

Answer 11

1) mostly empty space
2) 3 even smaller subatomic particles:
a) protons
b) neutrons
-> both joined together as nucleus at centre
c) electrons
-> surrounding nucleus in shells

Question 12

What is the radius of a nucleus?

Answer 12

~100,000 x less than the radius of an atom.

Question 13

What is the relative mass of a proton?

Answer 13

1

Question 14

What is the relative charge of a proton?

Answer 14

+1

Question 15

What is the relative mass of a neutron?

Answer 15

1

Question 16

What is the relative charge of a neutron?

Answer 16

0

Question 17

What is the relative mass of an electron?

Answer 17

0.0005

Question 18

What is the relative charge of an electron?

Answer 18

-1

Question 19

What does relative mean?

Answer 19

When comparing 2 quantities to each other, they are relative to each other:
-> if u js call mass of proton 1, mass of neutron also 1 (1.001 to 4.s.f.)

Question 20

What does every element have?

Answer 20

1) own name
2) chem symbol

Question 21

What does the full chemical symbol for an atom give?

Answer 21

Its chemical symbol & 2 no.s (atmoic & mass).

Question 22

What is the bottom number? (chemical symbol)

Answer 22

Atomic number for that atom.

Question 23

What is the atomic number?

Answer 23

The no. protons in its nucleus (& also no. e^-s, bc atoms are neutral overall).

Question 24

What is the number of protons equal to in an atom?

Answer 24

The atomic number & the no. e^-s in the atom (atoms have neutral charges overall).

Question 25

What is the full chemical symbol for a carbon-12 atom?

Answer 25

12C6

Question 26

What is the top number? (chemical symbol)

Answer 26

Mass number for that element.

Question 27

What is the mass number?

Answer 27

Total no. of protons & neutrons: mass number = no. protons (atomic no.) + no. neutrons

Question 28

Mass number = ?

Answer 28

Number of protons (atomic number) + number of neutrons

Question 29

What does 'A' represent?

Answer 29

Mass number.

Question 30

What does 'Z' represent?

Answer 30

Atomic number.

Question 31

What does 'X' represent?

Answer 31

Chem. symbol

Question 32

What are isotopes?

Answer 32

Isotopes of an element are atoms w/ same no. protons & e^-s but diff. no.s nuetrons. -> means have same atomic no. -> but diff. massno.

Question 33

How are isotopes identified?

Answer 33

Should be ID'd w/ full chem symbols -> but may see isotopes named after mass no., e.g. 2H1 is hydrogen-2.

Question 34

What is 3H1 known as?

Answer 34

Hydrogen-3.

Question 35

What are features of isotopes?

Answer 35

1) same atomic no. 2) diff. mass no. (diff. no. neutrons) 3) chem properties of element depend on no. e^-s in atoms 4) all isotopes of element have same no. e^-s so have identical chem properties 5) -> but diff. no.s neutrons may affect their physical properties, e.g. water vapour in air condenses & falls as rain more easily if its molecules contain 18O8 atoms, rather than 16O8 atoms

Question 36

What do the chemical properties of an element depend on?

Answer 36

The number of electrons in its atoms (so same as atomic no.).

Question 37

What are ions?

Answer 37

Charged particles.

Question 38

How are ions formed?

Answer 38

When atoms, or groups of atoms, lose or gain e^-s. -> can happen in chem. reactions

Question 39

What happens to an atom when it becomes an ion?

Answer 39

Gains or loses e^-s, so only no. e^-s changes, not no. protons (atomic no.) or neutrons.

Question 40

How did Dalton develop the atomic model?

Answer 40

1) 1803: John Dalton suggested all matter made from atoms 2) other scientists had suggested -> before, but Dalton's model was more detailed 3) -> also explained evidence from his xps on gases: a) all atoms of element are identical b) diff. elements contain diff. types of atom 4) Dalton didn't know wht atoms acc. were or if they even existed -> imagined them as tiny balls -> tech of his time didn't let him investigate in more detail

Question 41

What was the evidence Dalton's model explained?

Answer 41

From Dalton's xps on gases: 1) all atoms of element are identical 2) diff. elements contain diff. types of atom

Question 42

What was Dalton's model?

Answer 42

A solid-atom model; he imagined them as tiny solid balls. O

Question 43

How did Thomson develop the atomic model?

Answer 43

1) Joseph John (J.J.) Thomson discovered 1st subatomic particlle, the e^-, in 1897 2) in his xps, found that beams of 'cathode rays' changed direction in electric & magnetic fields 3) -> concluded cathode rays acc. tiny particles that were -vely charges & much smaller than atoms 4) his model has to make sense of 2 observations: a) atoms contain neutrons b) atoms neutral overall 5) in plum-pudding model, Thomson suggested atoms are spheres of +ve charge w/ e^-s dotted round inside like pieces of fruit in cake

Question 44

What was Thomon's atomic model?

Answer 44

Plum-pudding model; Thomson suggested atoms are spheres of +ve charge w/ e^-s dotted around inside like pieces of fruit in cake.

Question 45

Outline the plum-pudding model.

Answer 45

1) sphere of positive charge ("cake") 2) electrons ("fruit inside cake") -> (must label)

Question 46

How did Rutherford contribute to the development of the atomic model?

Answer 46

1) Enrest Rutherford worked w/ Hans Geiger & Ernest Marsden to test plum-pudding model 2) 1909: they ptd beams of +vely charged particles called alpha particles at thin gold foil 3) they expected the particles to go straight thru the foil -> most did -> -> but many changed direction slightly -> ~ even came straight back -> as if alpha particles 'd been pushed by something 4) Rutherford explained the results by suggesting atom has +vely charged nucleus containing most of its mass -> also suggested outside nucleus, e^-s would orbit like planets in solar system

Question 47

What was Rutherford's atomic model?

Answer 47

Planetary model: nucleus surrounded by 3 loops w/ electrons in them (remember to label)

Question 48

How did Bohr contribute to the development of the atomic model?

Answer 48

Niels Bohr realised orbiting electrons would be attracted to opp.ly charged nucleus & would rapidly spiral inwards. 1913: used math.al models to improve Rutherford's model. Bohr showed that e^-s occupy fixed energy levels, or shells, around nucleus.

Question 49

What was Bohr's atomic model?

Answer 49

Concentric circles (fixed energy levels or shell), w/ nucleus in middle. Oo. (remember to label)