Lecture 3 Chemistry Flashcards

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1
Q

Element

A

A substance that cannot be broken down into substances with different properties; composed of one type of atom

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2
Q

Fun Fact!

A

There are only 92 naturally occurring elements in the universe, the rest are man made

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3
Q

Atom

A

The smallest part of an element that displays the property of the element

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4
Q

Proton

A

Positively charged, 1 amu (atomic mass unit)

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5
Q

Neutron

A

No charge, 1 amu

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6
Q

Electron

A

Negatively charged, very low mass-negligible in calculations

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7
Q

Atomic Number

A

equal to the number of protons in each atom of an element

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8
Q

Mass Number

A

atom is equal to the sum of the number of protons and neutrons in atom’s nucleus

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9
Q

Atomic Mass

A

approximately equal to the mass number

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10
Q

Periods

A

arranged horizontally by increasing atomic number in rows called

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11
Q

Groups

A

Atoms of an element arranged in vertical columns are called

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12
Q

Isotopes

A

atoms of the same element that differ in the number of neutrons (and therefore different atomic masses)

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13
Q

The Distribution of Electrons

A

Bohr model

Electrons revolve around the nucleus in energy shells (energy levels).

For atoms with atomic numbers of 20 or less, the following rules apply:

  • the first energy shell can hold up to 2 electrons
  • each additional shell can hold up to 8 electrons
  • each lower shell is filled first before electrons are placed in the next shell
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14
Q

Valence Shell

A

outermost energy shell

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15
Q

Molecule

A

Two or more elements bonded together

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16
Q

Compound

A

a molecule containing at least two different elements bonded together

17
Q

Formula

A

tells you the number of each kind of atom in a molecule

18
Q

Ion

A

an atom that has lost or gained an electron

19
Q

Ionic bond

A

forms when electrons are transferred from one atom to another atom and the oppositely charged ions are attracted to one

20
Q

Covalent Bonds

A

when two atoms share electrons so each atom has an octet of electrons in the outer shell

21
Q

Nonpolar Covalent Bond

A

electrons are shared equally between atoms.

Examples: hydrogen gas, oxygen gas, methane

22
Q

Electronegativity

A

the ability of an atom to attract electrons towards itself in a chemical bond. Electronegativity is based on the number of protons-the greater the number of protons, the greater the electronegativity

23
Q

Hydrogen Bond

A

a weak attraction between a slightly positive hydrogen atom and a slightly negative atom

24
Q

Properties of Water

A

Water has a high heat capacity

Water has a high heat of vaporization

Water is a good solvent

Water molecules are cohesive and adhesive

  • Cohesion is the ability of water molecules to cling to each other due to hydrogen bonding
  • Adhesion is the ability of water molecules to cling to other polar surfaces
25
Q

Hydrophilic & Hydrophobic

A
  • Hydrophilic molecules dissolve in water.

* Hydrophobic molecules do not dissolve in water.

26
Q

Ph

A

a measure of hydrogen ion concentration in a solution

27
Q

Acids

A

substances that dissociate in water, releasing hydrogen ions

28
Q

Bases

A

substances that either take up hydrogen ions (H+) or release hydroxide ions (OH−)

29
Q

Ph scale

A
Used to indicate the acidity or basicity (alkalinity) of a solution.
•Values range from 0-14
•0 to <7 = Acidic
•7 = Neutral
•>7 to 14 = Basic (or alkaline)
30
Q

Buffer

A

a chemical or a combination of chemicals that keeps pH within normal limits