Bio-1406: Chapter 2

What are isotopes?

Different forms of the same element.
Same # protons, different # of neutrons.

What are radioactive isotopes?

An unstable isotope that releases particles or energy.

What is radioactive decay?

The spontaneous breakdown of an unstable atomic nucleus.

What causes radioactive decay?

An unstable nucleus loses particles and/or releases energy to become more stable.

What is released during radioactive decay?

Protons
Neutrons
Gamma
Radiation
High energy electron

What happens if radioactive decay changes the amount of protons?

The atom becomes a different element
Ex. Carbon-14 into Nitrogen-14.

What happens to carbon-14 radioactively decays?

It becomes Nitrogen-14.

What are 4 applications of radioisotopes?

Diagnostic tools, tracers, research, medicine

What makes radiation from radioisotopes harmful?

It can damage cellular molecules.

Why are electrons attracted to the nucleus?

Electrons are negatively charged, while nucleus is positively charged.

When an electron is far from the nucleus what does that do?

The electron now has a higher potential energy.

When an electron is closer to the nucleus what does that do?

The electron now has a lower potential energy.

What is potential energy?

Stored energy an object has because of it’s position/ arrangement. “Opportunity” for more movement, like ball at top of stairs vs. bottom.

What is an electron shell?

A fixed energy level where electrons can live around the nucleus.

What does an electron have to do to move to a higher shell?

Absorb energy.

What happens when an electron drops to a lower level?

It releases energy, appearing as light or UV.

What is the valence shell?

The outermost electron shell of an atom.

Why are valence shell electrons so important?

They largely determine an atom’s chemical behavior, and how it bonds.

Why do atoms with same number of valence shell electrons behave similar?

Their outermost electron arrangement interact with other atoms similar.

What is the octet rule?

All atoms want 8 electrons in their valence shell, they become more stable that way.

How can atoms satisfy the octet rule?

By donating/ accepting/ sharing electrons.

What makes an atom an ion?

When it has unequal # of protons and electrons, thus having a charge.

What is a cation?

A positive charged ion that lost one or more electrons.

What is an anion?

A negative charged ion that gained one or more electrons.

What creates an ionic compound?

THe attraction between positive charged ions and negative charged ions after electron transfer.

What happens to most ionic compounds in water?

They dissociate/ separate into individual ions.

What is the ionic-bond example involving sodium and chlorine?

Sodium looses electron to become Na ⁺
Chlorine gains an electron to become Cl ^-
Oppositely charged ions attract to become NaCl.

What is phrase to remember cation?

Cation = cats have paws (positive charge)
Cation = catastrophe (of loosing electron/s)!

What is a covalent bond?

A strong chemical bond between two atoms charing electrons.

What is phrase to remember covalent?

Co = together/ shared, coparents

Valent = valence shell electrons

Thus, covalent is sharing electrons together.

Why are covalant bonds important?

They form biological molecules found in cells.

What do covalent bonds do in water?

They are hydrophobic, not dissociating in water.

What is a nonpolar covalent bond?

A bond where electrons are shared equally.

What is a polar covalent bond?

A bond where electrons are NOT shared equally.

An example of a nonpolar covalent bond?

Oxygen, O₂, because 2 oxygen atoms share electrons equally.

Why is methane, CH₄, nonpolar?

Carbon shares an electron with 4 hydrogen, solving their single electron problem.

What causes partial charges in a polar covalent bond?

The shared electrons spend more time closer to one nucleus than the other. Thus- One becomes more positive, the other negative.

What does δ⁺ mean?

Slight partial charge.

What does δ^- mean?

Slight negative charge.

What is a hydrogen bond?

A weak attraction between a partially-positive (δ⁺) hydrogen and a nearby partially-negative (δ^-) electronegative atom.

Which atoms commonly form hydrogen bonds?

Oxygen and nitrogen.

What are van der Waals interactions?

Very weak attractions caused by temporary partial charges when atoms/ molecules are very close.

Why do weak attractions still matter?

Weak interactions help stabilize the shape and function of molecules.

What happens in a chemical interaction?

Chemical bonds broken/formed, changing composition of matter.

What do two opposite-facing arrows (⇌) mean in a chemical equation?

This is a reversible equation, processed in both directions.

What does it mean when one arrow in “⇌“ is longer?

That direction is favored.

What is chemical equilibrium?

A dynamic state where forward and reverse occur at the same rate.

What is a reactant concentration?

The amount of reactant present in given volume/ space.

How does a higher reactant concentration affect reaction rate?

It causes more frequent collisions, creating more opportunities for reactions.

Way to remember what higher reactant concentration means.

Put a bunch of kids in a room, more chance for them to fight.

Way to remember what lower reactant concentration means.

Put less kids in a room, less chance for them to fight.

How does an accumulating product affect a reversible reaction?

It makes the reversible reaction more frequent, must match.

Are reactants and products equal in amounts during chemical equilibrium?

No. the concentration just remains stable at consistent ratio.

Why is equilibrium called dynamic?

Reactions continue in both directions even though they stay stable. Dynamic is still doing.

What does it mean if equilibrium lies far to the right?

Most reactants have been converted to products, reaction has gone to completion.

How many elements are defined?

118.

How many elements occur naturally?

92.

How many elements are found in living cells?

<30.

How many elements are unstable/ theoretical?

26.

What % of natural elements are essential?

20-25%

How many natural elements are essential to humans?

25.

How many natural elements are essential to plants?

17.

What % of CHON (Carbon, Hydrogen, Oxygen, Nitrogen) is in living matter?

≅96% of living matter.

What % of CPPS (Calcium, Phosphorus, Potassium, Sulfur) is in living matter?

≅4% of living matter.

What trace elements are required in minute quantities?

Iron, Iodine, Zinc.

What is Arsenic?

Naturally occurring but toxic.