Chapter 2: The Nature of Molecules and the Properties of Water

Vocabulary flashcards covering foundational chemistry concepts from Biology 110 Chapter 2, including atomic structure, chemical bonding, isotopes, subatomic particles, and the properties of water.

Element

A pure substance made of only one type of atom that cannot be broken down into simpler substances.

Compound

A substance made from two or more different elements that are chemically bonded in a fixed ratio, can only be separated by chemcial means.

Mixture

A combination of two or more substances where each maintains its individual properties and can be physically separated.

Atom

The smallest unit of matter that retains all of an element's chemical properties.

Trace elements

Chemical elements present in organisms in very small amounts.

How many elements are essential for life?

25

Major elements of the human body

oxygen, carbon, hydrogen, and nitrogen.

Subatomic particle

A unit of matter or energy that is smaller than an atom, consisting of protons, neutrons, and electrons.

nucleus

The small, central region of an atom that contains protons and neutrons.

Matter

All of the substances in the universe that have mass and occupy space.

Atomic mass

The mass of the protons and neutrons contained within an atom.

Atomic number

The number of protons present in the nucleus of a given atom.

Mass number

the sum of the number of protons and neutrons in an atom's nucleus.

Electron

A negatively charged subatomic particle with almost no mass ($\frac{1}{1840}\text{ Dalton}$) located in orbitals surrounding the nucleus.

Orbital

The volume of space around the nucleus in which electrons are most often found.

Electrons _____ from the nucleus have more energy

farther

There are ___ elements in nature

92

Isotopes

Atoms of the same element that contain the same atomic number but differing numbers of neutrons and atomic masses.

Radioactive isotopes (Radioisotopes)

Unstable isotopes that decay with a nuclear breakup and emit significant amounts of energy.

PET scans

A medical diagnostic procedure that utilizes radioisotopes for imaging.

____ elements have all eight electrons

inert

atoms fill their ____ shells first

inner

______ shells have a maximum of two electrons

the _____ can have a maximum of eight electrons

two outermost shells

Ion

An atom or particle that carries a net positive or negative electric charge due to the loss or gain of electrons.

Redox Reaction

A chemical reaction involving the transfer of electrons between two species, leading to oxidation and reduction processes.

Oxidation

The process in which an atom or molecule loses electrons

Only ____ are directly involved in chemical activity

electron

Reduction

The process in which an atom or molecule gains an electron

electron shells

energy levels where electrons occur

Chemical bond

An attraction that holds atoms together in molecules or compounds to achieve stability.

Covalent bond

A very strong chemical bond formed when two atoms share one or more pairs of electrons.

cohesion

water molecules stick to other water molecules by hydrogen bonding

adhesion

water molecules stick to other polar molecules by hydrogen bonding

the pH scale ranges from ___

0-14

On the pH scale, is 0

most acidic

acid

any substance that dissociates in water to increase the H+

base

substance that provides either hydroxide (OH-) or other negatively charged ions that combine with H+ dissolved in water

On the pH scale, is 14

most basic

Ionic bond

formed by the attraction of oppositely charged ions; it is strong but breaks in water.

Hydrogen bond

A weak attraction formed between polar molecules due to partial positive and negative charges, such as between water molecules.

Octet rule

The chemical principle that atoms tend to interact in order to fill their outer energy level with eight electrons to achieve stability.

Periodic table

The arrangement developed by Mendeleev organizing elements by atomic mass, revealing recurring patterns of chemical properties in groups of eight.

Isomer

Molecules that have identical molecular formulas but differ in the spatial arrangement of their atoms.

pH

The measure defined as the negative logarithm of the hydrogen ion concentration ($[H^+]$) in a solution.

Buffer

A substance that acts as a reservoir for $H^+$ ions, resisting changes in concentration to maintain a stable pH.

without ___, your body cannot transport oxygen

iron

an ____ deficiency prevents production of thyroid hormones

iodine

energy loss that occurs when an unstable atom’s nucleus releases radiation

radioactive decay

living cells cannot distinguish between ___ of the same element

isotopes

neutral atoms have the same number of ____ and ____

electrons , protons

more protons than electrons = net positive charge

cation

fewer protons than electrons = net negative charge

anion

number of electrons in the outermost energy level

valence electrons

the number of electrons in the outermost shell determines the _____ _______ of the atom

chemical properties

atoms whose outer shells are not full tend to _____ with other atoms, participating in chemical reactions

interact

atoms that chemically react and bond to each other form _____

moleculestoma

atoms with _______ outer shells tend to react so that both atoms end up with _____ outer shells

incomplete, complete

the attraction for shared electrons

electronegativity

equal sharing of electrons

nonpolar covalent bonds

unequal sharing of electrons

polar covalent bonds

extent of chemical reaction is influenced by

temperature, concentration of reactants and products, catalysts

in liquid water, hydrogen bonds constantly ___ and ____

form, break

high specific heat, high heat of vaporization, solid less dense than liquid, good solvent, organizes nonpolar molecules, can form ions

properties of water