Atoms and electronic structure Flashcards
Nucleus
Ball of positive charge in the centre of an atom
Has protons and neutrons
Atomic number
The number of protons in an element
The small number on the periodic table
Mass number
The total number of protons and neutrons in an element
ALWAYS a full number
Can vary because there may be a different number of neutrons (isotopes)
Relative atomic mass
The large number for each element on the periodic table
The weighted average of commonly occurring isotopes
Isotopes
When an element has a different number of neutrons
Eg hydrogen 1 has 0 neutrons
Hydrogen 2 has 1 neutron
Hydrogen 3 has 2 neutrons
How to work out the relative atomic mass using isotopes?
(Mass number of isotope 1 x Percentage of abundance of isotope 1)
+
(Mass number of isotope 2 x Percentage of abundance of isotope 2)
Divide this by 100
How to find out the number of neutrons in an element?
Mass number - number of protons
What are the relative charges of each subatomic particle?
Electron = -1
Neutron = 0
Proton = 1
What are the relative mass of subatomic particles
Electron = almost 0
Proton = 1
Neutron = 1
Why is the number of electrons not included in the mass number?
Because the relative mass of an electron is very very close to 0
Radius of an atom
0.1 nm
(1 × 10⁻¹⁰m)
Radius of a nucleus
1x10⁻¹⁴m
Less than 1/10000 the radius of the atom itself
Plum pudding model
Ball of positive charge containing negative electrons floating around
Solid throughout and no empty space
No neutrons
Findings of the alpha scattering experiment
Most particles went straight through = particles are mostly empty space
Some particles changed direction = centre of an atom has a + charge causing them to repel
Some particles bounced back = the mass of an atom is concentrated at the centre (nucleus)
Nuclear model
Mostly empty space
Tiny nucleus with only positive charge
