Unit 1, Topic 3 - Bonding and Structure Flashcards
What types of substances usually form together to make ionic compounds?
Metal and non-metal
Describe ionic bonding
It is an electrostatic force of attraction between oppositely charged ions.
What can be said about the strength of ionic bonds?
They are strong
Why do atoms gain or lose electrons?
They are more stable with a full outer shell of electrons. When forming compounds atoms tend to have stable electron arrangement.
How do you work out how many electrons a metal loses when it forms an ion?
A metal loses electrons equal to the number of electrons in the outer shell.
A metal loses electrons equal to the number of electrons in the outer shell.
Why do metal ions do this?
They are more stable with a full outer shell of electrons.
What always happens when metal atoms form ions?
They lose electrons to form positive ions.
Write an equation to show how aluminium ions are formed from aluminium atoms.
Al —> Al 3+ + 3e-
2,8,3 2,8
What happens to non-metal atoms when they form ions?
They always gain electrons to become negative ions.
How do you work out how many electrons a non-metal atom gains when it forms an ion?
The number of electrons gained is the same as the number of electrons needed to fill the outer shell.
Know how to write nuclide notation for ions. E.g. How would you write the nuclide notation for a chloride ion with mass number 35?
35
Cl-
17
Know how to work out the number of protons, neutrons and electrons when given the nuclide notation of an ion. E.g. 27
Al 3+
13
protons+13
neutrons+14
electrons=10
What type of substances have metallic bonding?
Metals
Describe metallic bonding.
Electrostatic attraction between positively charged atom cores or ions and delocalised electrons.
What can be said about the strength of a metallic bond?
It is strong
What type of elements usually form covalent compounds?
Non-metal atoms
What is a covalent bond?
A shared pair of electrons
What holds the atoms together in covalent bonding?
(be able to draw diagrams)
The shared pair of electrons is attracted to both positive nuclei.
Be able to draw diagrams to show howthe outer electrons are shared in elements and compounds to from covalent bonds.
See notes and slides.
What is the formula for an oxygen molecule? How many bonds are there between atoms?
O2-2 shared pairs of electrons (we write the 2 smaller and at the bottom of the O.
What is a diatomic molecule?
A molecule that contains 2 atoms
What is a molecule?
A group of atoms held together by covalent bonds.
What are the 7 elements that exist as a diatomic molecule?
H2, O2, N2, F2, Cl2, Br2, I2
Which of the following molecules are diatomic?
HCl, H2O,NH3, CO, CO2
(be able to identify compounds that exist as diatomic molecules)
CO and HCl
What shape are diatomic molecules?
Linear
Look at LI 24-27
for drawing the shape of atom molecules.
What is meant by a discrete molecular substance?
One that exists with separate molecules.
What do most covalent substances exist as?
Discrete covalent molecules
What type of bonding is found in a molecule?
Covalent
Are covalent bonds inside molecules strong?
Yes, they are strong
Are the bonds (forces of attraction) between molecules strong?
No, they are weak
What term is used to describe bonds between molecules?
Intermolecular bonds/forces of attraction
What does the formula of discrete covalent substances tell you?
The actual number of atoms in the molecule.
Describe what is meant by a covalent network.
A giant structure where atoms are covalently bonded together.
What information does the formula of a covalent network give you?
e.g SiO2
Contains the simplest ratio of atoms of each element.
e.g for every Si atom there are 2 0 atoms.
Name 2 elements with a covalent network structure?
Silicon and Carbon (graphite and diamond)
Name 2 compounds with a covalent network structure?
Silicon dioxide and Silicon carbide.
What type of structure do ionic compounds have?
(look at diagram for LI 37)
Ionic compounds consist of a lattice of oppositely charged positive and negative ions. An ionic crystal lattice.
What information do you get from the formulae of an ionic compound?
e.g MgCl2
The ratio of each ion present in the ionic crystal lattice.
What is an electric current?
A flow of charged particles
What charged particles can carry a current?
Freely moving/ Delocalised electrons OR ions.
Why do metals and carbon (graphite) conduct electricity?
Metals and graphite both have delocalised electrons in their structure which are free to move.
Why do covalent compounds not conduct electricity?
Covalent compounds consist of molecules that are uncharged, they contain no charged particles (either ions or delocalised electrons to carry a current.)
In what state will ionic compounds conduct?
Ionic compounds don’t conduct in the solid state but do when dissolved in water or when molten.
Why do ionic compounds conduct when dissolved or molten but not when solid?
The ions are free to move when molten or dissolved but they are not free to move when solid as they are held in a lattice structure.
Why do metals have high melting and boiling points?
the delocalised electrons are attracted to many surrounding positive ion cores.
Why do ionic compounds have high melting and boiling points?
there is a strong electrostatic force of attraction between positive and negative ions.
Why do covalent network structures have high melting and boiling points?
the mutual attraction of the shared pair of electrons to both positive nuclei.
Why do discrete covalent molecular substances have low melting and boiling points?
Only weak force of attraction between molecules are broken when these substances melt/boil. The strong covalent bonds in the molecule are NOT broken.
What can be said of the solubility of ionic substances in water?
They are usually soluble.
Covalent substances may or may not soluble in water. What can those that are not be dissolved in?
Other covalent solvents such as hexane.
What do metals and non-metals usually form?
ionic bonds
How many non-metals usually form covalent bonds?
Two or more
What is an element?
A substance that is made of only one type of atom. A chemical element is a chemical substance that cannot be broken down into other substances.
What term is used to describe bonds between molecules?
“intermolecular forces are weak”
Covalent bonds inside molecules are strong whereas the bonds (forces of attraction) between molecules are weak.
What are some properties of ionic compounds?
High melting and Boiling Points, conduct in the liquid state ie dissolved in water, they do not conduct electricity in the solid state
Name the shape of some 3 atom molecules (containing 2 bonds).
Angular/bent
Name the shape of some 4 atom molecules (containing 3 bonds).
Pyramidal
Name the shape of some 5 atom molecules (containing 4 bonds).
Tetrahedral
