Learn: Unit 1 Notes 1: Chemistry | Quizlet

Matter

Anything that takes up space and has mass

Element

A substance that cannot be broken down into simpler substances by chemical reactions

Compound

A substance made up of atoms of two or more different elements in a fixed ratio

Molecule

Two or more atoms held together by covalent bonds

Trace Elements

Required by an organism in only minute quantities

Atom

The smallest unit of matter that still retains the properties of an element

Atomic Number

The number of protons in an atom

Mass Number

The total number of protons and neutrons in the nucleus of an atom

Atomic Mass

The weighted average of the masses of the isotopes of an element. Can be approximated by the mass number

Isotopes

Atoms of the same element that have different numbers of neutrons

Radioactive Isotopes

Decay spontaneously, giving off particles and energy

Valence Electrons

The chemical behavior of atoms depend on the number of electrons in the outermost electron shell

Valence Number

Determines the bonding properties of the atom

Covalent Bonds

Bonds created by sharing electrons with other atoms.

Ionic Bonds

Formed when one or more electrons are transferred from one atom to another. Electron transfer results in charged atoms called ions

Hydrogen Bonds

Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. In living cells the electronegative partners are usually oxygen or nitrogen atoms

Electronegativity

Is an atom's attraction for the electrons in a covalent bond

Nonpolar Covalent Bond

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity (Ex: O2, H2, N2, CH4)

Polar Covalent Bond

One atom is more electronegative, and the atoms do not share the electron equally (Ex: H2O)

Van der Waals Interactions

These charges allow all molecules and atoms to stick to one another when they are close together. These interactions are both very weak and strong, only occurring when atoms are close to each other

Chemical Reactions

The making and breaking of chemical bonds

Reactants

A starting material in a chemical reaction

Products

Ending materials in a chemical reaction.

Organisms are composed of...

matter

Matter is made up of...

elements

Life requires about __ chemical elements

25

Carbon, hydrogen, oxygen, and nitrogen make up __% of living matter

96

Most of the remaining 4% consists of...

calcium, phosphorus, potassium, and sulfur

Organisms cannot maintain ___________ if they have a deficiency in some essential elements of life (Nitrogen or Iodine Deficiency)

Homeostasis

Diatomic molecules have...

nonpolar covalent bonds

Neutrons have a ________ charge.

neutral or no

Protons have a _______ charge.

positive

Electrons have a ________ charge.

negative

Some applicants of radioactive isotopes in biological research are:

- Dating fossils

- Tracing atoms through metabolic processes

- Diagnosing medical disorders

Atoms are __________ (inert) when the valence orbital is full

Unreactive

Valence for hydrogen

1

Valence of oxygen

2

Valence of nitrogen

3

Valence of carbon

4

Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms. These interactions can form...

Chemical bonds

Anions are...

negative ions

Cations are...

positive ions

Ionic bonds are strong in their _____________ form but have weak attractions in ________

crystallized, solution

Kind of bonds that make up the side of the DNA molecule:

Phosphodiester bonds

Kind of bonds that hold the two sides of DNA together:

Hydrogen bonds

As electrons move around, they create ever changing "___ _____" of positive and negative charges around the molecule.

hot spots

A molecule's _____ is usually very important to its function.

shape

Biological molecules recognize and interact with each other with a ___________ based on molecular shape.

specificity

Molecules with similar shapes have _______ __________ _______

similar biological effects

Chemical equilibrium is reached when _____.

forward and reverse reaction rates are equal