chap 3 key terms

Question 1

allotrope

Answer 1

o Allotrope- Different forms of the same element in which the atoms combine in different ways.

Question 2

amorphous

Answer 2

o Amorphous- A structure that has no consistent arrangement of particles.

Question 3

asymmetrical molecule

Answer 3

o Asymmetrical molecule- A molecule in which the polar bonds are unevenly (or asymmetrically) distributed. The bond dipoles do not cancel and an overall molecular dipole is created.

Question 4

combustion

Answer 4

o Combustion- A rapid reaction with oxygen accompanied by the release of large amounts of heat: also called burning.

Question 5

covalent bond

Answer 5

o Covalent bond- The force of attraction formed when one or more pairs of electrons are shared between two nuclei.

Question 6

covalent lattice

Answer 6

o Covalent lattice- A 3D lattice structure formed from covalently bonded non-metal atoms.

Question 7

covalent network lattice

Answer 7

o Covalent network lattice- An arrangement of atoms in a lattice in which there are strong covalent bonds between the atoms in all three dimensions.

Question 8

covalent layer lattice

Answer 8

o Covalent layer lattice- an arrangement of atoms in a lattice in which there are strong covalent bonds that have formed in a layer.

Question 9

diamond

Answer 9

o Diamond- A form of pure carbon that is the hardest naturally occurring substance.

Question 10

diatomic molecule

Answer 10

o Diatomic molecule- A molecule formed from two atoms only, e.g. Cl2.

Question 11

dipole

Answer 11

o Dipole- The separation of positive and negative charges in a molecule.

Question 12

dipole-dipole attraction

Answer 12

o Dipole-dipole attraction- A form of intermolecular force that occurs between polar molecules where the partially positively charged end of one molecule is attracted to the partially negatively charged end of another molecule.

Question 13

dispersion force

Answer 13

o Dispersion force- the force of attraction between molecules due to temporary dipoles induced in the molecules. The temporary dipoles are the result of random fluctuations in the electron density.

Question 14

double covalent bond

Answer 14

o Double covalent bond- A covalent bond in which four electrons (two electron pairs) are shared.

Question 15

electron density

Answer 15

o Electron density- The concentration of electrons that usually refer to the regions around an atom or molecule.

Question 16

electron group

Answer 16

o Electron group- A region of negative charge around an atom, which could be either different types of covalent bonds or a non-bonding pair.

Question 17

electronegativity

Answer 17

o Electronegativity- The ability of an atom to attract electrons in a covalent bond towards itself.

Question 18

graphite

Answer 18

o Graphite- A form of carbon in which the carbon atom are arranged in layers.

Question 19

hydrogen bond

Answer 19

o Hydrogen bond- A type of intermolecular, dipole-dipole force where a hydrogen atom is covalently bonded to a highly electronegative atom such as oxygen, nitrogen or fluorine. Due to the disparity of electronegativity values between the atoms involved, the hydrogen develops a partial positive charge and bonds to lone pairs of electrons on neighbouring atoms of oxygen, nitrogen or fluorine.

Question 20

instantaneous dipole

Answer 20

o Instantaneous dipole- A net dipole formed in a molecule due to temporary fluctuations in the electron density in the molecule.

Question 21

intermolecular force

Answer 21

o Intermolecular force- an electrostatic force of attraction between molecules, including dipole-dipole forces, hydrogen bonds and dispersion forces.

Question 22

intramolecular force

Answer 22

o Intramolecular bond- a force that holds the atoms within a molecule together

Question 23

Lewis structur

Answer 23

o Lewis structure- electron dot structure.

Question 24

molecular formula

Answer 24

o Molecular formula- A formula of a compound that gives the actual number and type of atoms present in a molecule. It may be the same as or different from the empirical formula.

Question 25

molecule

Answer 25

o Molecule- A group of two or more atoms covalently bonded together, and representing the smallest fundamental unit of a chemical compound.

Question 26

non-bonding electron

Answer 26

o Non-bonding electron- An outer-shell electron that isn’t shared between atoms.

Question 27

non-polar bonds

Answer 27

o Non-polar bonds or molecules that don’t have a permanent dipole. They have an even distribution of charge.

Question 28

permanent dipole

Answer 28

o Permanent dipole- A net dipole formed in a molecule to permanent differences in electron density due to electronegativity differences between atoms and overall asymmetry in the molecule.

Question 29

polar

Answer 29

o Polar- bonds or molecules with a permanent dipole. They have an uneven distribution of charge.

Question 30

polarity

Answer 30

o Polarity- The measure of how polar a molecule or bond is. The difference in charge between the positive and negative ends of an electric dipole. The difference in charge between the positive and negative ends of a polar molecule or covalent bond.

Question 31

polyatomic molecule

Answer 31

o Polyatomic molecule- a molecule that consists of more than two types of atoms, e.g. H2O

Question 32

pyramidal

Answer 32

o Pyramidal- A molecular shape formed when there are four electron groups and one non-bonding pair around a central atom.

Question 33

Sublimation

Answer 33

o Sublimation- The process by which a substance goes directly from the solid phase to the gaseous phase, without passing through a liquid phase.

Question 34

single covalent bond

Answer 34

o Single covalent bond- A covalent bond in which two electrons are shared between two nuclei. It is depicted in a valence structure as a line between the two atoms involved.

Question 35

structural formula

Answer 35

o Structural formula- A formula that represents the 2D arrangement of atoms in a molecule and shows all bonds, as well as all atoms.

Question 36

symmetrical molecule

Answer 36

o Symmetrical molecule- A molecule in which the polar bonds are evenly distributed. The bond dipoles cancel out and do not create an overall molecular dipole.

Question 37

temporary dipole

Answer 37

o Temporary dipole- A net dipole formed in a molecule due to temporary fluctuations in the electron density in the molecule.

Question 38

tetrahedral

Answer 38

o Tetrahedral- The shape of a molecule with a central atom surrounded by four other atoms. The bond angle between two outer atoms and the central atom is 109.5O.

Question 39

trigonal planar

Answer 39

o Trigonal planar- A molecular shape formed when there are 3 electron groups and no non-bonding pairs around a central atom.

Question 40

triple covalent bond

Answer 40

o Triple covalent bond- A covalent bond in which six electrons are shared between two nuclei. It is depicted in a valence structure as 3 lines between the 2 atoms involved.

Question 41

Valence shell electron pair electron (VSEPR) theory

Answer 41

o Valence shell electron pair electron (VSEPR) theory- a model used to predict the shape of molecules. The basis of VSEPR is that the valence electron pairs surrounding an atom mutually repel each other, and therefore adopt an arrangement that minimises this repulsion, thus determining the molecular shape.