1830041
Description
Flashcards by Jem Kinney, updated more than 1 year ago
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Created by Jem Kinney
almost 10 years ago
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| 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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