Ap Bio Unit 1 Chapter 2

Matter

• Anything that takes up space and has mass

• Ex) rocks, metals, oils, gases

Element

• A substance that cannot be broken down

• 92 elements that occur in nature

• Ex) copper, carbon, oxygen

Compound

• Substance consisting of two or more different elements in a fixed ratio

• Ex) H20 = 2:1 ratio, NaCl = 1:1 ratio

Element vs. Compounds

• Both are pure substances

• Elements are made up of 1 atom and cannot be broken down chemically

• Compounds are made up of 2 or more atoms and can be broken down chemically

Essential Elements

• Elements that that an organism needs to live a healthy life and reproduce

• Out of 92 natural elements there is about 20%-25%

• Varies per organism

• Humans need 25

• Plants need 17

Trace Elements

• Required by an organism in only small quantities

• Varies per organism

• Ex) Iron is needed by all forms of life but Iodine is only needed for vertebrates (animals with backbones)

Atom

• Smallest unit of matter that still retains the properties of an element

Neutrons

• Neutrally charged subatomic particle

• Found in nucleus

• Contributes to mass w/ protons

Protons

• Positively charged subatomic particle

• Found in nucleus

• Gives an element its identity

• Contributes to mass w/ neutrons

Electrons

• Negatively charged subatomic particle

• Surrounds the Nucleus

Atomic Nucleus

• Dense core in the center of the atom

• Made up of protons + neutrons

Dalton

• Unit of measurement

• Name comes from John Dalton

• Same as atomic mass unit (amu)

• Neutrons + protons have masses close to 1 dalton

Atomic Number

• # of protons

• # of electrons in a neutrally charged atom

• Written as subscript left to element symbol

Mass Number

• Total # of protons + neutrons

• Written as a superscript to the left of element symbol

Atomic Mass

• Total mass of an atom

• Ex) Mass number of Na is 23 but its total mass is 22.9898 daltons

Atomic Mass vs Atomic Number

• Atomic mass is the total mass of an atom (neutrons + protons)

• Atomic Number is based only on the # of protons (distinguishing the element)

Isotopes

• Different atomic forms of the same element

• Same # of protons but different # of neutrons

• Different masses

Radioactive Isotopes

• Isotopes where the nucleus decays spontaneously, giving off particles of energy

• Leads to a change in the # of protons which changes it to an atom of a different element

• Ex) carbon-14 has a neutron decay into a proton changing it to nitrogen-14

Half-life

• The time it takes for 50% of the parent isotope to decay into its daughter isotope

Radiometric Dating

• Scientists measure the ratio of different isotopes and calculate how many half-lives (in years) have fossilized or a rock was formed

• Idk if we need to know this???

Energy

• The capacity to cause change by doing work

Potential Energy

• The energy matter possesses because of its location or structure

Valence Electrons

• Outermost electrons

• Valence shell: outermost shell

• Determines chemical behavior and interactions

• Atoms give or gain their valence electrons

Orbital

• Three-dimensional space where electrons are found 90% of the time

• No more than 2 electrons in a single orbital

Chemical Bond

• An attraction between atoms where the atoms either share or transfer their valence electrons

Covalent Bond

• The sharing of a pair of valence electrons

Single Bond

• 1 pair of shared electrons

Double Bond

• Two pairs of shared electrons

Electronegativity

• The attraction of a particular atom for the electrons of a covalent bond

• How much “pull” it has

Nonpolar Covalent Bond

• When two atoms with similar electronegativity are bond

• Bonds are shared equally

• Symmetric

Polar Covalent Bond

• When an atom is bonded to a more electronegative atom

• Bonds unequally shared

• Asymmetric

Oxygen Gas

O₂

Carbon Dioxide

CO₂

Glucose

C6H1206

Phosphate

PO₄^3-

Ammonia

NH₃

Water

H₂O

Ionic vs Covalent Bonds

• Ionic is when a metal & non-metal transfer their electrons

• Covalent is when two non-metals share their electrons

Hydrogen Bond

• Non-covalent bond between a hydrogen and an electronegative atom

• Hydrogen has a partial positive charge that allows it to be attracted to a different electronegative atom with a partial negative charge

Van der Waals Interactions

• Individually weak and occur when atoms and molecules are very close together

• Changing regions of positive and negative charge that enable all atoms and molecules to stick together

• When many interactions occur simultaneously, they can become powerful

• Ex) gecko lizard can climb up a wall with its interactions between the foot anatomy and the wall

Chemical Reactions

• Changes in composition of matter

• Reactants: starting material (left of arrow)

• Products: resulting materials (right of arrow)

• Chemical equilibrium: the reactions offset one another exactly