BIOL Exam 1 Study Guide (1-15)

What are the characteristics of life?

All living things:

• Made of cells

• Use energy (metabolism)

• Maintain homeostasis

• Grow & develop

• Reproduce

• Respond to stimuli

• Evolve

Phosphorus has an atomic number of 15 and an atomic weight of 33. How many neutrons does phosphorus have?

• Atomic # = protons

• Mass # = protons + neutrons

• Neutrons = mass − atomic #

👉 Phosphorus:
33 − 15 = 18 neutrons

List and give examples of each level of life organization.

Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem

Put these in order from the least to the most complex: elephant, trunk, muscles, amino acids, proteins, and atoms.

Atoms → Amino acids → Proteins → Muscles → Trunk → Elephant

Be able to define: Solvent vs solute vs solutions

• Solvent = does dissolving (water)

• Solute = gets dissolved (salt)

• Solution = mixture

Be able to list and give examples of all three domains of life

Eukarya: Organisms with a nucleus (protists, fungi, plants, animals)

Archaea: Single-celled prokaryotes often found in extreme environments (e.g., methanogens, thermophiles, Halobacterium).

Bacteria: Single-celled prokaryotes with peptidoglycan walls (e.g., E. coli, Staphylococcus aureus, cyanobacteria)

Be able to determine and define: the atomic mass, atomic number, proton #, Electron #, neutron #

Atomic Number: The total number of protons in the nucleus; it defines which element you are looking at.

Proton Number: This is the same as the Atomic Number.

Electron Number : In a neutral atom, this equals the number of protons

Atomic Mass: The average mass of an element, representing the sum of protons and neutrons.

Neutron Number : The neutral particles found by subtracting the protons from the mass

List the above (5) and the symbol for Sodium

1. Symbol: Na (derived from the Latin word natrium).

2. Atomic Number: 11 (meaning it has 11 protons).

3. Classification: Alkali Metal (Group 1 of the periodic table).

4. Physical Appearance: A soft, silvery-white metal that can be cut with a knife.

5. Reactivity: Highly reactive; it reacts vigorously (and often explosively) with water

Location and charges of an atom’s subatomic particles

• Protons (+) in nucleus

• Neutrons (0) in nucleus

• Electrons (−) outside

• Neutral atom: protons = electrons

• Shells:

  • 1st = 2 electrons

  • 2nd = 8 electrons

Stable atoms: full outer shell
Reactive: not full

How many electrons do the first 2 electron shells hold?

The first electron shell () holds a maximum of 2 electrons, and the second electron shell () holds a maximum of 8 electrons.

When are atoms stable and inert? When are they reactive?

when their outermost electron shell (valence shell) is completely filled, typically with eight electrons

What is an isotope? Give an example.

atoms of the same element that have the same number of protons but different numbers of neutrons. (Ex, 1. Hydrogen Isotopes
Hydrogen has three common isotopes based on neutron count:)

Describe the proton and electron number for a neutral atom.

the number of protons in the nucleus is exactly equal to the number of electrons surrounding it. Because each proton has a charge and each electron a charge, this equality ensures the total electrical charge of the atom is zero.

Compare and contrast electrons in an ionic versus a covalent bond.

Ionic bonds involve the complete transfer of valence electrons from a metal to a non-metal, creating charged ions attracted to each other, while covalent bonds involve the sharing of valence electron pairs between non-metal atoms. Ionic electrons reside primarily on one atom, whereas covalent electrons are shared between nuclei

Why is water polar? Be sure to describe the electrons and how they are shared.

due to an unequal sharing of electrons between oxygen and hydrogen atoms, creating a "bent" shape with distinct electrical charges. Because oxygen is far more electronegative, it strongly attracts shared electrons, creating a partially negative charge at the top and partially positive charges at the bottom