Bonding Flashcards
Mass number =
Top number
Total number of protons and neutrons
Atomic number
Bottom number
Number of protons
How are compounds formed
Two or more elements chemically joined together
What are isotapes
Different atomic forms of the same element, which have the SAME number of PROTONS but DIFFERENT number of NEUTRONS
Ionic bonding
Atoms LOSE or GAIN electrons to form CHARGED particles (called ions)
Ionic compounds
- Have regular ionic lattices
- Form a closely packed regular lattice arrangement
- Similar properties
Ionic compounds properties
- high melting & boiling points (strong attraction)
- melt -> free to move
- carry electrical current
- dissolve easily
Which groups are most likely to form ions
Groups
1 & 2
6 & 7
Ions have the electronic structure of a
Noble gas
What happens to group 1 and 2 elements
They lose electrons to form positive ions
What happened to group 6 and 7
The gain elections to form negative ions
What forms an ionic compound
Positive ions combine with negative ions to form ionic compounds
Wha is the overall charge of any compound
Zero
The negative charges ——- the positive charges
Balance
E.g. Na+ and Cl- = +1 + -1 = 0 The charges are balanced to for NaCl
What is covalent bonding
Sharing electrons with other atoms
Both atoms have a full outer shell
Substances with covalent bonds can either be —–
Simple molecules or giant structures
Explain a simple molecular structure
- Atoms have strong bonds
- Forces of attraction are weak
- Melting & boiling points are low (easily parted)
- Don’t conduct electricity
- No ions or electrical charge
Giant covalent structures are
Macromolecules
Giant covalent structures
- Atoms are bonded by strong covalent bonds
- High melting and boiling points
- Don’t conduct electricity
- Example - diamond
Metallic structures
- Consists of giant structures
- Have free electrons -> good heat and electricity conductors
- Allow layers to slide over each other/bent/shaped
Alloys are harder than
Pure metals
Pure metals
- Have different sized atoms
- Distort the layers
- More difficult for layers to slide over each other
Draw the ionic structure of Sodium Chloride
Na+ Cl-
Draw the ionic structure of calcium oxide
Cl- Ca2+ Cl-
Draw the covalent bond of Hydrogen and Chlorine
H-H Cl-Cl
Simple molecules definition
A few atoms held together by strong covalent bonds.
An example is carbon dioxide (CO2), the molecules of which contain one atom of carbon bonded with two atoms of oxygen.
Properties of simple molecular substances
Low melting and boiling points
This is because the weak intermolecular forces break down easily.
Properties of simple molecular substances
Non-conductive
they do not have any free electrons or an overall electric charge.
Giant covalent structures definition
- Contain a lot of NON- METAL ATOMS joined to adjacent atoms by covalent bonds.
- Atoms are arranged into giant regular lattices - extremely STRONG STRUCTURES because of the many bonds involved.
Properties of giant covalent structures
Very high melting points
a lot of strong covalent bonds must be broken. Graphite, for example, has a melting point of more than 3,600ºC.
Properties of giant covalent structures
Variable conductivity
Diamond does not conduct electricity. Graphite contains FREE ELECTRONS , so it DOESN’T conduct electricity. Silicon is semi-conductive - that is, midway between non-conductive and conductive.
Metals have a
Giant structure
Why do metallic bonds have free electrons
Produce all the properties of metals
Where do free electrons come from
The outer shell of every atom in the structure
Metals are
good conductors of HEAT and ELECTRICITY
How do electrons hold atoms together
They have strong forces of electrostatic attraction between positive metal ions and negative electrons
