Atomic Structure and Bonding Flashcards
John Dalton
- 1808
- all elements made up of small, indivisible particles (atoms)
- atoms cannot be created or destroyed
- atoms of different elements = different properties
J.J. Thompson
- 1897
- discovered electron
- suggested atom was neutral - equal positive and negative charges
- “plum pudding model”
plum pudding model 
Negative electrons are embedded in a sphere of positive charge
Ernst Rutherford
- 1913
- proved atoms consisted of electrons revolving around a positively charged nucleus
- named positive charges protons
James Chadwick
- 1932
- nucleus has two different types of particles
- neutral particle called neutron
- difficult to detect - no charge
Relative mass of proton
1
Relative charge of proton
+1
Where is the proton located?
Nucleus
Relative mass of neutron
1
Relative charge of neutron
0
Where is the neutron located?
Nucleus
Relative mass of electron
1
—-
1840
Relative charge of electron
-1
Where is the electron located?
Shells
Atomic number
Number of protons in the nucleus of an atom - smaller number
Mass number
Total number of protons and neutrons in the nucleus of an atom - larger number
charge of an atom
- as a whole an atom has no electrical charge
- equal numbers of protons and electrons cancel each other out
Group number
- number of electrons in the outer shell
- horizontal columns
Period number
- number of shells in use
- vertical columns
Radius of an atom
distance between centre of nucleus and furthest electron from nucleus
How big is an atoms radius?
0.1 nanometres (nm)
- 1 x 10-9 m
- 1000000000 nm = 1m
Radius of nucleus is less than 1/10000 th of atom
Isotope
atoms that have the same number of protons (so they are atoms of the same element), but they have a different number of neutrons (so they have a different mass number).
Relative atomic mass (Ar) of chlorine
The mass number of chlorine is given as 35.5 in the periodic table because it is the average mass taking into account the two isotopes
75% 35 Cl and 25% 37 Cl
Ar = (35 x 75) + (37 x 25)
—————————- = 35.5
100
Allotropes
- different forms of the same element in the same state
- e.g Carbon = diamond, graphite and graphene
- chemically similar to isotopes because they have the same number of electrons
Cation
- Positive ion
- metals lose electron to form them
Anion
- Negative ion
- Non-metals gain electrons to form them
Why do ions form?
- All elements what to achieve the stability of a nobel gas
- They can achieve this by having a full outer shell of electrons
What are ions?
Charged particles formed when atoms lose or gain electrons to achieve a full outer shell
What do ions have the same electronic structure as?
A noble gas
What is the number of a charges on an ion equal to?
The valency
Molecular ions
Charged particles containing more than one atom
E.g sulfate ion SO4 -2
Chemical bonding
if an atom doesn’t have a full outer shell of electrons it will react with another atom to achieve a full outer shell
How many types of chemical bonding are there?
Three:
- ionic
- covalent
- metallic
How does an ionic bond form?
- occurs between metals and non-metals
- ionic bonds form when a metal transfers electrons to a non-metal
- forming positive and negative ions
What is an ionic bond?
The electrostatic force of attraction between oppositely charged ions
They are strong and require a substantial amount of energy to break them
