Chemical Bonding. Flashcards
What is chemical bonding?
The joining, chemically of two or more atoms to form a compound.
What is an ion?
An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons.
Why would an atom loses or gain electrons in the outermost shell?
This loss or gain of electrons takes place to gain a full outer shell of electrons.
Ionisation of metals and non-metals:
Metals: all metals lose electrons to other atoms to become positively charged ions.
Non-metals: all non-metals gain electrons from other atoms to become negatively charged ions.
What holds the positive and negative charges of ionic compounds together?
The positive and negative charges are held together by the strong electrostatic forces of attraction between opposite charges.
What is an ionic bond?
An ionic bond is the electrostatic force of attraction between positive and negative ions.
What happens when an atom loses an electron?
When an atom loses an electron it forms positively charged ions called cations.
What happens when an atom gains electrons?
When an atoms gains electrons it forms negatively charged ions called anions.
What is a lattice structure?
A regular arrangement of alternating positive and negative ions.
How do you describe the forces of attraction between the positive and negative ions of a giant lattice structure?
The forces of attraction between the positive and negative ions of a giant lattice structure are very strong.
What are the 3 physical properties of ionic compounds?
- Ionic compounds have high melting and boiling points.
- Ionic compounds are soluble in water but insoluble in organic solvents.
- Ionic compounds conduct electricity only when molten or when dissolved in water because the ions are mobile.
Why do Ionic compounds have a high melting and boiling point?
Because a lot of heat energy is required to break the strong force of attraction..
Why are ionic compounds soluble in water but not organic solvents?
They are soluble in water because the water molecules are able to separate the ions from one another and keep the ions in solution.
When are covalent compounds formed?
Covalent compounds are formed when electrons are shared between atoms.
What are the properties of covalent compounds?
- Covalent compounds have low melting points and boiling points because the intermolecular attractive forces are weak.
- Covalent compounds are insoluble in water but can dissolve in organic substances.
- Covalent compounds do not conduct electricity because they have no free electrons or ions.
What are the allotropes of carbon?
Diamond and graphite are allotropes of carbon that have giant covalent structures.
What are the three properties of diamonds?
- Diamond does not conduct electricity
- Diamond has very high melting and boiling point.
- Diamond is extremely hard and dense
What is diamond used in?
Diamond is used in jewellery and as cutting tools.
In a diamond, how is a giant tetrahedron covalent structure formed?
Each carbon atom bonds with four other carbons, forming a tetrahedron.
What are the three properties of graphite?
- Graphite conducts electricity.
- Graphite has a very high melting point.
- Graphite is soft and slippery.
What are the covalent bonds of a diamond like.
All the covalent bonds in diamonds are identical and strong with no weak intermolecular forces.
Why does graphite conduct electricity?
The free electrons that exist in between the layers and are free to move and carry charge, hence graphite can conduct electricity.
In graphite, how is a giant hexagonal covalent structure formed?
Each carbon atom is bonded to three others forming layers of hexagonal-shaped forms, leaving one free electron per carbon atom.
Why is graphite slippery and smooth?
The covalent bonds within the layers are very strong but the layers are connected to each other by weak intermolecular forces, hence the layers can slide over each other making graphite slippery and smooth.
