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44 Cards in this Set
- Front
- Back
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What must occur for a chemical bond to take place? |
There must be forces between atoms; attractive and repulsive forces |
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Where do attractive forces exist? |
Between the nucleus and electrons of one; as well as the nucleus of one and electrons of another |
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Where do repulsive forces exist? |
Between two positive nuclei of the atoms and negative electron clouds of the atoms |
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What has to occur before a new bond can occur? |
The existing bonds between original compounds must be broken. The broken, separate particles are at a unstable high energy state |
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How do bonds break? |
They take up energy and break. The energy is released when new bonds occur |
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Why don't noble gases bond? |
They don't have half filled orbitals |
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How do covalent bonds occur? (3) |
-They occur mainly between non-metals -Occurs when two atoms bond by sharing pairs of electrons - They have half filled orbitals that overlap; forming a new orbital |
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How does a non-polar bond occur? |
When two of the same atoms bond (electronegativities will equal zero) |
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How does a polar covalent bond occur? |
-When the atom with higher electronegativity attracts shared electrons more than the other atom - causes an asymmetrical electron cloud around the nuclei of the two atoms |
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What is a dipole molecule? |
A molecule that has two poles |
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How does ionic bonding occur? |
- Difference in electronegativity between two atoms is so big that no sharing of electrons occurs. The electrons are therefore transferred from one atom to the other - The new ions attract and form a crystal lattice |
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How are electrons transferred? |
They transfer from the atom with low electronegativity to the one with the high |
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What determines the ratio in which ions pack together? |
The ionic charge |
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Name the properties of an ionic bond (3) |
- have high melting and boiling points - do not conduct electricity in solid phase - will conduct electricity in liquid phase (since ions are free to carry it) |
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Define metallic bonds |
The attraction of forces between positive metal ions and sea of delocalised electrons |
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How does a metallic bond occur? (3) |
- atoms are close together; causing outer orbitals to overlap - valence electrons delocalize and move around adjacent orbitals - remaining positive ions form an attractive force with delocalized electrons |
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What are must be present for a metallic bond to occur? (2) |
- low ionization energy of atoms - empty valence orbitals (for electrons to move) |
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Why are metals malleable and good conductors of heat and electricity? |
They are good conductors due to delocalised electrons They are malleable since the atoms glide across each other |
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Which are the only elements in nature that exist as mono-atomic elements? |
The noble gases eg. Helium, neon, argon etc. |
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How is a compound formed? |
When two or more atoms of different elements attract by strong forces |
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What are the types of compounds? (3) |
- molecular compounds (by covalent bonding) - ionic compounds (by ionic bonding) - metallic compounds (by metallic bonding) |
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What is the name of the solid that forms by ionic bonding? |
An ionic substance |
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What elements do ionic substances consist of? |
Both metallic and nonmetallic elements |
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What is an empirical formula?
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It is a chemical formula that shows the simplest ration between atomsin a compound.
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What do empirical formulas NOT show? |
They don't show much of compound itself |
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When is empirical formula's helpful? |
When looking at covalent network structures and is impossible to identify exactly how many atoms are bonded together |
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What is the molecular formula? |
It is a chemical formula that shows both the number and type of atoms in the bond |
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What is a structural formula? |
It is a formula that shows the arrangement and the bonds of the atoms in a compound |
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What are the different types of diagram models to show compounds in? (3) |
- circle diagrams - space filling model - ball - and - stick model (ball represents atom, stick represents bond) |
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How can a molecule be presented? |
As a molecular formula |
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What can solid substances with covalent molecular structures be composed of? |
Atoms,molecules or ions
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Where do strong intramolecular forces exist? |
Between atoms of the molecule
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Where do weak intermolecular forces exist? |
Between the molecules |
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What are covalent network structures? (2) |
Structures where the covalent bonds extend through outthe structure of the substance.
- this means the structure consists of a repeating structure of bonded atoms |
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What forms an atomic lattice? |
Covalent network structures that are mainly
composed of covalent solids |
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What are examples of a covalent network structures |
Graphite, silicon, diamond |
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What are the characteristics of covalent network structures? |
- high melting and high boiling points - very strong intramolecular forces |
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What are allotropes? |
Different forms of the same element who have different structures and different chemical and physical properties. This is due to the different bonding arrangements |
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What are ionic substances? |
Solids that form by strong electrostatic forces between oppositely charged ions |
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What are the builing blocks of ionic crystal lattice ? |
Individual ions |
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What is closest packing? |
The tightly packed metal atoms in either 'cubic closest packing' or 'hexagonal closest packing' |
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Describe cubic closest packing |
- less tightly packed, forms a cube - iron, potassium and sodium are in a cubic structure |
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Describe hexagonal packing |
- Tightly packed; each atom surrounded by six other atoms - Two elements that have hexagonal packing is zinc and magnesium |
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Define kenetic energy |
Energy that is possessed by an object in motion. It increases with temp as the molecules will be moving faster colliding more |
