AS Chemistry bonding

Jem Kinney
Flashcards by Jem Kinney, updated more than 1 year ago
Jem Kinney
Created by Jem Kinney over 6 years ago
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A-Level chemistry (Unit 1) Flashcards on AS Chemistry bonding, created by Jem Kinney on 01/02/2015.

Resource summary

Question Answer
why do chemical bonds form? So atoms can achieve a more stable arrangement by achieving a full outer energy level.
when does ionic bonding occur? when a non-metal and metal atom bond together.
what is ionic bonding? the electrostatic forces of attraction between oppositely charged ions.
what are the properties of ionically bonded compounds? They form giant structures so they have high boiling points. They conduct electricity when molten or dissolved in water. Ionic compounds are brittle.
Why are ionic compounds brittle? Because they form a lattice of alternating positive and negative ions. A blow in a sideways direction may move the ions and produce contact between ions with like charge.
What is a covalent bond? A pair of electrons shared between two non-metal atoms that holds the atoms together.
how does a covalent bond work? electrostatic forces of attraction between the nuclei and the shared electrons holds the molecule together.
What is a double covalent bond? a covalent bond where four electrons are shared.
what are the properties of substances with a molecular structure? -low melting points - poor conductors of electricity even when dissolved in water. -
what is co-ordinate bonding? covalent bonding where a lone pair of electron is donated by one atom to an electron deficient atom.
how is co-ordinate bonding represented on a diagram? As an arrow pointing away from the donor.
What is meant by the term electronegativity? Electronegativity is the power of an atom to attract the electron density in a covalent bond towards itself.
What does electronegativity depend on? - nuclear charge - the distance between the nucleus and the outer shell electrons - the shielding of the nuclear charge by electrons in inner shells.
what are the trends in electronegativity? - as we go up a group in the periodic table electronegativity increase. - as we go across a period in the periodic table, the electronegativity increase.
what is the bond property known as polarity? polar describes a molecule in which the charge is not symmetrically distributed so one area is slightly positively charged and another is slightly negatively charged.
What is the polarity of a covalent bond between two atoms that are the same? the bond is non-polar.
What is the effect of electronegativity on polarity? the greater the difference in electronegativity, the greater the polarity
what is a metallic bond? electrostatic forces of attraction between positive ions and de-localised electrons
What does the strength of metallic bonds depend on? - the greater the charge on the ion the greater the number of de-localised electrons - the size of the ion; the smaller the ion, the closer electrons are to the positive nucleus and the stronger the bond.
what are the properties of metals. -they are good conductors of electricity and heat -metals are malleable and ductile -metals have high melting points -metals are shiny
what are the three types of intermolecular force? - van der waals forces -Dipole-dipole forces -Hydrogen bonding
how do dipole- dipole forces arise? when molecules with permanent dipole come near to each other, they will change orientation to attract one another.
how do Van der Walls forces arise? they act between all molecules as a result of the temporary charges.
how do Van der Waals forces effect boiling temperatures? They cause a rise in boiling temperatures.
what is needed for hydrogen bonds occur? - a hydrogen atom that is bonded to a very electronegative atom. - a very electronegative atom with a lone pair of electrons.
why do NH3 h20 and HF have higher boiling points than expected? Because the hydrogen bonds add strength and forces that need to be broken.
what are the energy changes occur when solids melt and liquids vaporise? energy is supplied to increase the kinetic energy of the molecules
What energy changes occur when liquid is vapourised? additional energy is added to the particles in order to raise the kinetic energy.
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