atomic structure C 1.2

Question 1

what is an atom

Answer 1

the smallest particle of an element that still has its chemical properties

Question 2

what is a molecule

Answer 2

made from two or more atoms joined together. they are joined by attractive forces called chemical bonds.
the atoms in a molecule can be all the same or they can be different

Question 3

size of an atom

Answer 3

is given by its atomic radius which is half its diameter. a bond length is the distance between the centres of two joined atoms

Question 4

what is inside an atom

Answer 4

• protons and neutrons joined together as the nucleus at the centre
• electrons surrounding the nucleus in shells

Question 5

radius of a nucleus

Answer 5

is about 1 000 000 times less than the radius of an atom

Question 6

mass number calculation

Answer 6

atomic number (no of protons) + number of neutrons

Question 7

what are isotopes

Answer 7

elements of atoms with the same number of protons and electrons but different numbers of neutron

( have the same atomic number but their mass number is different )

Question 8

what are isotopes like

Answer 8

the chemical properties of an element depends on the number of electrons in its atoms : all the isotopes of an element have the same number of electrons so they have identical chemical properties

however the different number of neutrons may affect their physical properties

Question 9

what are ions

Answer 9

charged particles that have lost or gained electrons

Question 10

what did john dalton do (1803)

Answer 10

• suggested that all matter is made from atoms
• all atoms of an element are identical
• different elements contain different types of atoms

Question 11

what did thompson do (1897)

Answer 11

• discovered the first subatomic particle, the ELECTRON
  atoms contain electrons and atoms are neutrall overall
  plum pudding model : atoms are spheres of positive charge with electrons dotted around inside

Question 12

what did rutherford do (1909)

Answer 12

• pointed beams of positively charged particles ( alpha particles) at the thin gold foil
• atom has a positively charged nucleus containing most of its mass
• outside the nucleus, electrons orbit like planets in a solar system

Question 13

what did bohr do (1913)

Answer 13

• realised that orbitting electrons would attracted to the oppositely charged nucleus and would rapidly spiral inwards.
• showed that electrons occupy fixed energy levels or shells around the nucleus