Structure and Bonding Flashcards
What’s a covalent bond?
A shared pair of electrons between two atoms
What type of atoms are they formed between
Non-metal
What is the difference in electronegativity in pure covalent bonding/non-polar covalent bonding? (Example?)
Small/no difference so they have an equal ‘pull’ on the shared electrons
elements like H2(two atoms covalently bonded together) and hydrocarbons
When are polar covalent bonds formed?
When the attraction of the atoms for the pair of bonding electrons is different
What difference in electronegativity does polar covalent bonding have?(examples?)
Medium difference
H2O, H-Cl, NH3
In a polar covalent bond what charge does the atom with the higher electronegativity have and vice versa?
Higher electronegativity- negative charge S-
Lower electronegativity-postive charge S+
What’s an ionic bond?
The electrostatic attraction between positive and negative ions
What are the partial charges on atoms in a polar covalent bond called?
A permanent dipole
What structures do ionic compounds form?
Lattice structures of oppositely charged ions
What’s is the difference in electronegativity in an ionic bond? (Examples?)
Large difference
Na+Cl-, Mg2+(Cl-)2
What types of atoms typically bond in an ionic bond? Why?
Metal and non-metal as metal has a low electronegativity value and non-metal has a high electronegativity value
Some metal compounds can also be covalent
How is ionic formulae written?
Simplest ratio of each type of ion in the substance
Example- Na+Cl- tells us that fro every sodium ion there’s one chloride ion
Mg2+(Cl-)2 tells us that there are two chloride ions for every magnesium ion
What compound would usually be the most ionic(have a high ionic character)?
A compound with a large difference in electronegativity
What three factors decide whether a compound is ionic or covalent?
1) ionic compounds will conduct electricity when molten or when dissolved in water(solution), covalent compounds don’t conduct
2)ionic compounds tend to have high melting points(lots of energy is needed to break the strong ionic bonds existing in the ionic lattice)
3) ionic compounds are usually soluble in water
What types of melting points do covalent compounds have(network and molecular), what state would they be at room temp?
Network-high melting points so solid at room temp
Molecular-low melting+boiling points so gas/liquid at room temp
Would polar covalent or non polar substances be more likely to dissolve in water?
Polar covalent substances are more likely to be soluble as they have charges inside the substance
Non-polar will dissolve in non polar substances
(LIKE DISSOLVES LIKE)
Comment on the conductivity of metal covalent and ionic compounds as a solid, liquid and solution
Solution Liquid Solid
Metal-Metals Y Y don’t dissolve in water
Covalent- X X X
Ionic- Y Y X
What do all molecular elements and compounds and monatomic elements do at sufficiently low temperatures? What’s needed for this to occur?
Condense and freeze
Attractive forces must exist between the molecule/discrete atoms
What are ionic compounds, covalent network compounds, and covalent molecules held together by in the solid state?
Ionic- ionic bonds
Covalent network-covalent bonds
Covalent molecules-intermolecular forces/van der waals forces
What are the three main types of van der waals forces, which are temporary which are permanent?
1-London dispersion forces(LDFs) temporary
2-Permanent dipole-permanent dipole interactions (permanent)
3-Hydrogen bonding(permanent)
What are London dispersion forces?
They are forces of attraction that can operate between all atoms and molecules
How are LDFs formed?
They’re formed as a result of an electrostatic attraction between a temporary and induced dipole Cuase by the uneven distribution of moving electrons within atoms and molecules
What molecules do PD-PD interactions occur between?
Polar molecules
What are PD-PD interactions?
Additional electrostatic forces of attraction between polar molecules
