Bonding Flashcards
What is a cation?
A positive ion
What is an anion?
A negative ion
What is an ionic bond?
When positive and negative ions are held together strongly by electrostatic forces of attraction in a giant lattice structure.
What is the explanation for why an ionic substance has a high melting and boiling point?
The electrostatic forces of attraction between cations and anions are strong in a giant lattice, requires a lot of energy to overcome
What is the explanation for why ionic substances are hard but brittle?
Because they have strong bonds between the positive and negative ions, BUT if the lattice distorts the ions repel and the structure breaks
What is the explanation for why ionic substances are generally soluble in water?
Water is polar so the ions are attracted to it
What is the explanation for why ionic substances don’t conduct electricity in the solid state?
The charged particles (ions) cannot move
What is the explanation for why ionic substances conduct electricity as liquids?
The ions are free to move
What happens when metals react with non metals?
1) the metal atoms lose electrons
2) the non metal atoms gain electrons
3) an ionic compound is made
EXAMPLE QUESTION:
magnesium oxide has a higher melting point than sodium chloride - explain why this is the case
Stronger bonds - the attraction between Mg and O is stronger in bigger charges due to larger electrostatic charges - more electrons have been exchanged
differences between simple covalent and giant covalent;
Simple; composed molecules - contain several atoms bonded strongly together by covalent bonds
Giant; contain million of atoms bonded by many strong covalent bonds to form a giant lattice
are the IMF of covalent bonds strong or weak?
weak IMF between molecules - little energy needed to overcome
are the bonds of covalent bonds strong or weak?
strong - lots of energy is needed to break them
What is the explanation for why covalent substances have low melting and boiling points and why many are liquid or a gas at room temperature?
IMF are weak so little energy is needed to separate electrons
What is the explanation for why covalent substances have poor electrical conductivity?
no charged particles to move
What is the explanation for why covalent substances have poor solubility in water?
no charges so no attraction to polar water
what is a covalent bond?
strong electrostatic forces of attraction between two nuclei and a shared pair of electrons
Why do diamond and graphite have different physical properties?
in diamond each C is bonded to 4 other carbons, in graphite only 3
description of a diamond structure;
each C atom is joined to 4 others by strong covalent bonds throughout the whole structure
description of a graphite structure;
each C atom is joined to 3 others within a layer, strong covalent bonds throughout a layer, weak intermolecular forces between layers
are diamond structures hard?
very hard - bonds are strong in all directions
are graphite structures hard?
soft between the layers as the IMF are weak
Diamond electrical conductivity?
none - no charges no ions
graphite electrical conductivity?
good conductor - delocalised electrons
Why do diamond and graphite have high melting point?
because diamonds have strong bonds in all directions and graphite has strong bonds in the layers, takes a lot of energy to break strong bonds
what are atoms in metals held together by?
metallic bonds
Explanation for why metallic bonds have high melting and boiling points?
because strong electrostatic forces between cations and delocalised electrons need lots of energy to break
Explanation for why metallic bonds are malleable and ductile?
layers of ions can slide over eachother
Explanation for why metallic bonds are good conductors of electricity?
delocalised electrons are able to move
Explanation for why metallic bonds are good conductors of heat?
because delocalised electrons carry kinetic energy through the lattice
What are alloys?
mixtures of metals where the different metals are metallically bonded in a giant metal lattice
why aren’t alloys regarded as compounds?
they don’t have a specific ratio and can be separated by physical means. Elements in an alloy react how the separate elements react
