BIO 201 Module 3 | The chemical context of life

Define Matter

Anything that takes up space and has mass

Define elements

A pure substance of only one kind of atom | The ice cream parlor

Define Molecules

Two or more atoms joined together (e.g O2, H2O) | 2 scoops of a flavor like chocolate and vanilla

Define compounds

A molecule with more than 1 element | Having more than 1 scoop (choco, vanilla, and strawberry)

Define Atoms

Smallest amount of an element (e.g. O, C, H) | the flavors in an ice cream shop

Define subatomic particles: protons, neutrons, and electrons

• Protons are positively charged and determine the element and atomic number.

• Neutrons have no charge and determine isotope, but with protons

• Electrons are negatively charged, determine the chemical reactivity, and orbit nucleus in a cloud

How do you determine atomic mass?

protons x neutrons

Define isotopes

elements that differ in their numbers of neutrons and, therefore, their atomic masses

Stable isotopes vs Unstable isotopes

Stable isotopes do not “lose” subatomic particles, unstable or radioactive isotopes decay spontaneously, releasing particles and energy

Electrons are arranged in _____ that surround the atomic nucleus

shells

Define valence electrons

The electrons in the outermost shell of an atom that are involved in bonding.

electrons have different energy levels with______ having greater potential energy

Outer shells

How much can the inner shell hold?

up to 2 electrons and the rest can hold up to 8

Atoms with incomplete valence shells are _______

Reactive

Atoms with complete valence shells are ________

Inert

Explain the octet rule

Atoms tend to gain, lose, or share electrons to have eight electrons in their outer shell, which makes them more stable.

What are essential elements?

Chemical elements that are necessary for the growth, development, and maintenance of living organisms. (O, C, H, N)

What are trace elements?

essential elements required by living organisms in very small amounts (ex: Iron, iodine, and selenium.)

What is molecular formula?

A formula that shows the exact number of each type of atom in a molecule. For example, H2​O indicates 2 hydrogen atoms and 1 oxygen atom.

What is electronegativity?

A measure of how strongly an atom is able to attract electrons to itself.

What does electronegativity depend on?

The atomic number (positively charged protons attract electrons ) and the atomic radius (distance of valence electrons from nucleus)

Differences in electronegativity….

…create bonds in which electrons are shared “equally” or “unequally.”

What are the different chemical bonds

1. Covalent bonds (polar and non-polar)

2. Ionic bonds

3. Hydrogen bonds

Define covalent bonds

A type of chemical bond where two atoms share one or more pairs of electrons.

Define non polar molecules

Molecules with an even distribution of charge, where electrons are shared equally and there are no distinct positive or negative ends.

Define nonpolar covalent bonds

A type of covalent bond where electrons are shared equally between atoms

Define polar molecules

Molecules with an uneven distribution of charge, creating a positive end and a negative end due to polar covalent bonds.

Define polar covalent bonds

A type of covalent bond where electrons are shared unequally between atoms causing partial charges in atoms.

Define hydrogen bonds

A weaker version of ionic bond. An attraction between a hydrogen atom bonded to a more electronegative atom (like oxygen or nitrogen) and another electronegative atom.

What are Ions?

Atoms or molecules that have gained or lost electrons and thus have a positive or negative charge.

What are anions

Ions with a negative charge, formed by gaining electrons.

What are cations?

Ions with a positive charge, formed by losing electrons.

Define Ionic bonds

Strong connections formed between positively charged cations and negatively charged anions due to electrostatic attraction.