BIO 108 Chp. 2

how does an element differ from a compound

A compound is a substance consisting of two or more elements in a fixed ratio. A compound has characteristics different from those of its elements.

double bond

A double covalent bond, or double bond, is the sharing of two pairs of valence electrons

what is an element

substance that cannot be broken down to other substances by chemical reactions.

What are van der Wall interactions? Are they strong or weak

Molecules or atoms that are very close together can be attracted by fleeting charge differences. These weak attractions are called van der Waals interactions. Collectively, such interactions can be strong, as between molecules of a gecko's toe hairs and a wall

Why are weak bonds important in biology

Most of the strongest bonds in organisms are covalent bonds that form a cell's molecules. Weak chemical bonding within and between molecules is also important. Weak chemical bonds reinforce shapes of large molecules and help molecules adhere to each other. Molecules may adhere temporarily by weak bonds - the reversibility of weak bonding can be an advantage.

anion

Negative charged ion

What are the subatomic particles that comprise an atom

Neutrons (no electrical charge) Protons (positive, (+) charge) Electrons (negative (-) charge) Electrons form a cloud around the nucleus. Neutrons and Protons have masses close to 1 Dalton.

single bond

single covalent bond, or single bond, is the sharing of one pair of valence electrons.

amino acid

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energy

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mass

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potential energy

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trace element

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What determines the shape of a molecule and why is shape an important consideration in determining how biologically important molecules interact

A molecule's shape is usually very important to its function. A molecule's shape is determined by the positions of its atoms' valence orbitals. In a covalent bond, the s and p orbitals may hybridize, creating specific molecular shapes.

What is the atomic number of an element? What does it tell us

All atoms of a particular element have the same number of protons in their nuclei. This is called the atomic number. 2He, 6C etc. It tells us the number of protons and electrons in an electrically neutral atom.

What happens when an atom's valence shell is full

An atom with a completed (full) valence shell is unreactive.

What is the mass number? What does it tell us

An element's mass number is the sum of protons plus neutrons in the nucleus. 2He, and is an approximation of the total mass of an atom, called its atomic mass.

What is an electron orbital and what is its relationship to an electron shell

An orbital is the three-dimensional space where an electron is found 90% of the time. Each electron shell consists of a specific number of orbitals. No more than two electrons can occupy a single orbital.

matter

Anything that makes up space and has mass. Made up of elements.

What is the relationship between bonding capacity and the number of unpaired electrons in an atom's valence shell

Bonding capacity (valence) usually equals the number of unpaired electrons in the valence shell.

What is an isotope?

Isotopes are two atoms of an element that differ in the number of neutrons in the nucleus. Therefore, their mass numbers will be different.

What is an electron shell?

Each shell has a characteristic average distance (from nucleus) and energy level.An electron can change the shell it occupies by absorbing and losing energy in exact amounts - the difference in energy between the energy levels of the two shells.

cation

Positive charged ion

What is an ionic bond and how does it differ from a covalent bond

Sometimes two atoms are so unequal in their attraction for valence electrons the more electronegative atom may strip electrons away from its partner. An example is the transfer of an electron from sodium to chlorine. After the transfer of an electron, both atoms have charges.

What is the outermost electron shell called and why is it important

The chemical behavior of an atom depends mostly on the number of electrons in its outermost shell. These electrons are called valence electrons and the shell they occupy is called the valence shell.

What is the difference between a nonpolar and polar covalent bond

a nonpolar covalent bond, the atoms share the electron equally. In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally.

electronegativity

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

What is a hydrogen bond? weak or strong?

hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. Weak

What is a covalent bond?

the sharing of a pair of valence electrons by two atoms.

atom

the smallest unit of matter that still retains the properties of an element. Composed of sub atomic particles.