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

How many naturally occurring elements are there

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

A chemical bond formed between 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.