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Flashcards in Unit 2 Deck (38):
1

Atom

Smallest unit of an element that contains all the characteristics of that element

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Electron

Subatomic particle with one unit of negative charge and negligible mass

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Proton

One unit of positive charge and mass close to 1 Dalton

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Neutron

Neutral with a mass close to 1 dalton

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Atomic number

Number of protons in an atom of a specific element

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Atomic mass

Sum of the masses of protons and neutrons in an atom

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Orbital

A region around the nucleus of an atom with a high probibility of containing an electron

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Ion

Any atom or molecule containing an unequal number of electrons and protons and therefore carrying a net positive or negative charge

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Cation

Positively charged ion

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Anion

Negatively charged ion

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Isotope

Different forms of the same element with the same number of protons but a different number of neutrons

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Radioactive isotope

An isotope that is unstable and undergoes radioactive decay, releasing energy

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Half-life

The time it takes for one-half of the atoms in a sample of a radioactive isotope to decay

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Energy level

A descrete level, or quantum, of energy that an electron in an atom possesses. To change energy levels, an electron must absorb or release energy

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Oxidation

Loss of an electron by an atom it molecule, associated with the gain of oxygen or a loss of hydrogen

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Valence electron

An electron in the outermost energy level of an atom

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Octet rule

Rule to describe patterns of chemical bonding in main group elements that require a total if 8 electrons to complete their outer electron shell

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Compound

A molecule that contains atoms of more than one element

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Ionic compound

Compound formed based on ionic bonds between two oppositely charged ions that forms a crystalline matrix, such as NaCl

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Electronegativity

Affinity of the nuclei for valence electrons

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Nonpolar

Covalent bonds that involves equal sharing of electrons

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Polar covalent bonds

A covalent bond in which electrons are shared unequally due to differences in Electronegativity of the atoms involved

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Hydrogen bond

A weak association formed with hydrogen in polar covalent bonds. Positive hydrogen is attracted to negative atoms

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Cohesive

Holding together; describes the tendency of water molecules to cling to each other due to hydrogen bonding

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Surface tension

A tautness of the surface of a liquid, caused by the cohesion of the molecules of a liquid. Water has very high surface tension

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Adhesion

The tendency of water to cling to other polar compounds due to hydrogen bonding

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Specific heat

The amount of health that must be absorbed or lost by 1 gram of a substance to raise or lower it's temperature 1 C

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Heat of vaporization

Amount of energy required to change 1 gram of a substance from a liquid to a gas

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Hydration shell

A "cloud" of water molecules surrounding a dissolved substance, such as sucrose or Na+ an Cl- ions

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Hydrophobic

Nonpolar substances not soluble in water

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Hydrophilic

Substances that are soluble in water

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Hydrophobic exclusion

Tendency of nonpolar molecules to aggregate together when placed in water. Exclusion refers to the action of water in forcing these molecules together.

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pH scale

A scale used to measure acidity and basicity

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Mole

Weight of 6.02 times 10 to the 23rd molecules

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Molar concentration

Concentration expressed as moles of a substance in 1 liter of pure water

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Acid

Any substance that dissociates on water to increase the hydrogen ion concentration and thus lower ph

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Base

Any substance that dissociates in water to absorb and decrease the hydrogen ion and raise the pH

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Buffer

A substance that resists changes in pH