Anatomy and Physiology CH2 Biochemistry Sec 1 (2.1-2.3)

Mass

The amount of material in matter

What is the smallest stable unit of matter

An atom

What are atoms composed of?

Subatomic particles, such as protons, neutrons, and electrons.

What electrical charge does a Proton, Neutron, and Electron have?

Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.

Where is the Nucleus in an atom? What does it contain?

Located in the center ; Contains one or more protons and may also contain neutrons

How is the mass of an atom determined?

By the number of protons and neutrons within the nucleus.

What do electrons do in the atom? What is then created?

The electrons in the atom whirl around the nucleus and create an electron cloud.

How does a molecule form?

When atoms interact and produce larger, more complex structures

Electrically neutral

equal number of protons and electrons

isotope

Atoms whose nuclei contain the same number of protons, but different number of neutrons

how do you designate isotopes?

The mass number ; Mass numbers are useful because they tell us the number of subatomic particles in the nuclei of different atoms

what unit is used to express atomic weight?

amu also known as dalton

Element

pure substance made of only one type of atom.

Describe trace elements

Trace elements are elements that an organism needs in very small amounts to stay healthy and function properly.

how is it possible for 2 samples of hydrogen to contain the same number of atoms yet have different weights?

This is because hydrogen has different isotopes; Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.

what is an electron shell?

An electron shell is a region around an atom’s nucleus where electrons are found.

explain electron shells and energy levels

Electron shells are the regions where electrons are found, and energy levels describe how much energy those electrons have.

Reactive elements

easily combine with other elements because their outer electron shell isn't stable ; EX: Sodium (Na), Chlorine (Cl) Hydrogen (H), Lithium (Li)

Inert elements

are elements that don't react easily with other elements; EX: Helium (He), Neon (Ne), Argon (Ar)

What largely determines how reactive an element is?

The number of valence electrons (electrons in the outer shell) largely determines how reactive an element is

How do elements with unfilled outermost energy levels (reactive elements) achieve stability? What is the result?

By gaining, losing, or sharing electrons to fill their outermost energy level; The atom is no longer electrically neutral, it now has more protons than electrons (a net positive charge)

Cation

an ion with a positive charge; It forms when an atom loses one or more electrons

Anion

An anion is an ion with a negative charge; It forms when an atom gains one or more electrons

What is a chemical bond and when or how does it occur?

A chemical bond is the force that holds two or more atoms together and occurs when atoms interact in a way that makes the overall system more stable

chemical reaction

a process where atoms rearrange their electrons and/or connections to form new substances. The bonds that form during the reaction then hold the atoms together in the new substance

Ionic bond

forms when one atom transfers electrons to another atom;

Example: Sodium chloride (NaCl)

Na gives 1 electron to Cl:

Na → Na⁺

Cl → Cl⁻

Then Na⁺ and Cl⁻ attract each other

Covalent bond

forms when atoms share electrons; Usually, this happens between nonmetal atoms.

Example: Water (H₂O)

Oxygen shares electrons with two hydrogen atoms. This allows the atoms to have more stable outer energy levels.

Molecule

A molecule is a group of two or more atoms held together by chemical bonds.

For example:

H₂ → 2 hydrogen atoms bonded together → a hydrogen molecule

O₂ → 2 oxygen atoms bonded together → an oxygen molecule

H₂O → 2 hydrogen atoms + 1 oxygen atom → a water molecule

indicate the maximum number of electrons that can occupy each of the first 3 electron shells (energy levels) of an atom

1st: 2

2nd: 8

3rd: 8 (really 18, but 8 to simplify)

explain why the atoms of inert elements do not react with one another or combine with atoms of other elements

Inert elements do not react easily because their outermost electron shell is already full, making them stable

For example:

Helium: 2 electrons → first shell is full

Neon: 2, 8 → outer shell is full

Argon: 2, 8, 8 → outer shell is full

explain how anions and cations form

Anions and cations form when atoms gain or lose electrons

A cation is a positively charged ion.

It forms when an atom loses electrons

An anion is a negatively charged ion.

It forms when an atom gains electrons

Compound

chemical substance made up of atoms of 2 or more different elements, regardless, of the type of bonding joining them

Ion

An ion is an atom or group of atoms that has an electrical charge because it has gained or lost electrons

For example:

Na → Na⁺ → sodium loses 1 electron → positive ion

Cl → Cl⁻ → chlorine gains 1 electron → negative ion

Nonpolar molecule

A nonpolar molecule has an even distribution of electrical charge, with no distinct positive or negative end.

Polar molecule

electrons are shared unevenly and the molecule has slightly positive and negative regions

Single covalent bond

Two atoms share 1 pair (2 electrons)

Example: H₂

H — H

The two hydrogen atoms share one pair of electrons

Double covalent bond

Two atoms share 2 pairs (4 electrons).

Example: O₂

O = O

The two oxygen atoms share two pairs of electrons

polar covalent bond

a covalent bond where the electrons are shared unequally between two atoms.

This happens because one atom attracts the shared electrons more strongly than the other.

For example, in H₂O:

H — O — H

Oxygen attracts the shared electrons more strongly than hydrogen does. So the electrons spend more time closer to oxygen.

This gives:

Oxygen a slightly negative charge (δ−)

Hydrogen a slightly positive charge (δ+)

nonpolar covalent bond

covalent bond where the electrons are shared equally or nearly equally between the atoms.

Example: H₂

H — H

Both hydrogen atoms attract the shared electrons equally because they are the same element. So neither atom becomes significantly positive or negative

hydrogen bond

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

It usually happens when hydrogen is covalently bonded to oxygen (O), nitrogen (N), or fluorine (F).

Example: Water 💧

In a water molecule (H₂O), oxygen pulls the shared electrons closer to itself:

Hδ⁺ — Oδ⁻ — Hδ⁺

The slightly positive hydrogen of one water molecule is attracted to the slightly negative oxygen of another:

Hδ⁺ — Oδ⁻ ··· Hδ⁺ — Oδ⁻

The ··· represents the hydrogen bond

Is a hydrogen bond the same as a covalent bond?

No, A hydrogen bond is not the same as a covalent bond.

Covalent bond → holds atoms together within a molecule

Hydrogen bond → creates an attraction between molecules (in many common examples)

Describe the kind of bonds that hold the atoms in a water molecule together

Polar covalent bonds where electron are shared unequally

Why can we apply the term molecule to the smallest particle of water, but not that of table salt?

The term molecule refers only to chemical structures held together by covalent bonds. Table salt is an ionic compound whose components sodium ions and chloride ions are held together by ionic bonds