Bonding- Chemistry Flashcards
What are ions?
- charged particles
- can be single atoms or groups of atoms
When do negative ions form?
- when atoms gain electrons
- they have more electrons than protons
When do positive ions form?
- when atoms lose electrons
- they have more protons than electrons
What are group 1,2,3 elements?
- metals
- they lose electrons to form positive ions
What are group 5,6,7 elements?
- non metals
- gain electrons to form negative ions
What do elements in the same group all have?
- the same number of outer electrons
- so they all form ions with the same charge
When a group 1 metal and a group 7 non metal react together what happens?
- metal atom loses electrons to form a positive ion
- non metal gains these electrons to form a negative ion
What are the oppositely charged ions strongly attracted to each other by?
- electrostatic attraction
- this attraction is called an ionic bond
What are ionic compounds made up of?
- positively charged part
- negatively charged part
What is the ionic charge of any compound?
- zero
- all the negative charges in the compound must balance all the positive charges
How are ions held together in ionic compounds?
- giant ionic structure
- ions are held together in a closely packed 3D lattice arrangement
- by the reaction between oppositely charged ions
Why is the electrostatic attraction between oppositely charges ions very strong?
- lot of energy is needed to overcome the strong attraction
- have a high melting and boiling point
What does each covalent bond provide?
- one extra shared electron for each atom (sharing pairs of electrons)
What is covalent bonding?
- strong electrostatic attraction between the negatively charged shared electrons (the bonding pair) and the positively charged nuclei of the atoms involved
How are the molecules in simple molecular substances?
- atoms within a molecule are held together by very strong covalent bonds
- forces of attraction between the molecules are very weak
Why are the melting/boiling points are very low for simple molecular substances?
- because the molecules are easily separated
Why are intermolecular forces stronger between molecules with a high relative molecular mass than between smaller molecules?
- there are more points along the larger molecules for intermolecular forces to act between them
- so more energy is needed to break the forces
What are the properties of giant covalent structures?
- all atoms bonded by strong covalent bonds
- lots of bonds so takes a lot of energy to break them
- so giant covalent are solids with very high melting and boiling points
- insoluble in water
- don’t conduct electricity (not even when in molten)
What is diamond made up of?
- network of carbon atoms that each form four covalent bonds
Why does diamond have a high melting point?
- strong covalent bonds take a lot of energy to break
How are the atoms held in diamond?
- strong covalent bonds hold the atoms in a very rigid lattice structure so its really hard
Why does diamond not conduct electricity?
- no free electrons or ions
What does each carbon atom form in graphite?
- each carbon atom only forms three covalent bonds creating layers of carbon atoms
How are the layers of carbon atoms held together in Graphite?
- held together weakly by intermolecular forces, so are free to slide over each other
- this makes graphite soft and slippery
