Chemistry 1

The reactions must be

"balanced."

When one of the atoms in a bond has a much higher electronegativity than the other, they do not share the electron pair equally. This results in

"polarity" across the bond and forms a polar covalent bond.

a pH of ___ is neutral a pH over ___ is basic a pH under ___ is acidic

7

Hydrogen bonds form when

a hydrogen atom that is already in a polar bond is attracted to another atom with a partial negative charge.

Hydrogen bonds form because

a polar covalent bond leaves the hydrogen atom with a partial positive charge and the other atom with a partial negative charge.

The pH of human blood is right about 7.4. If the pH changes to 6.9, then the blood is becoming more Question options: negative basic acidic positive ionic

acidic

Elements tend to fill their outermost shells with

electrons.To do this, they can either donate or accept electrons from other elements.

An atom can also be called protein proton element electron

element

And since all life is constantly interacting with water, you rarely see anything in a living organism forming an

ionic bond

Because of their charge, positive and negative ions are attracted to each other just like the opposite poles of two magnets. This holds the two atoms together in an

ionic bond. An example is NaCl or table salt.

After the transfer, both atoms are no longer neutral but have charges and are called

ions

Any substance that reduces the hydrogen ion concentration in a solution

is a base

Water (H2O)

is a compound in which two hydrogen atoms form single covalent bonds with an oxygen atom. Oxygen has 8 electrons, but two of them are in the first shell and six are in the valence shell. Sharing one electron with each of the two hydrogen atoms satisfies the valences of the oxygen and the hydrogens.

Methane (CH4)

is a simple compound that satisfies the valences of both C and H. Carbon has six electrons, so two in the first shell and four in the valence shell. The four hydrogen atoms each share a single electron with carbon's four single electrons. Carbon now has filled its outermost shell with eight electrons and is stable!

An acid

is a substance that increases the hydrogen ion concentration in a solution.

A covalent bond

is formed when two atoms share a pair of valence electrons. For example, hydrogen has only one electron. So its electron is sitting in the closest shell, which has room for two electrons. Put a second hydrogen atom next to it. It also only has one electron. The two atoms are both unstable at the moment because they have partially filled shells.

Nuclear Reaction

is one where you add or subtract neutrons and protons from the nucleus.

An electron shell Question options: describes the number of protons in an atom has nothing to do with covalent bonds is unstable if not completely full has 5 electrons

is unstable if not completely full

A molecule can form a hydrogen bond if Question options: it contains oxygen or nitrogen it contains benzene it contains sodium it contains only carbon it contains only hydrogen

it contains oxygen or nitrogen

Water is an effective solvent because

it readily forms hydrogen bonds with charged and polar covalent molecules. For example, when a crystal of salt (NaCl) is placed in water, the Na+ cations (ions of positive charge) interact with the partial negative charges of the oxygen regions of water molecules. The Cl− anions (ions of negative charge) interact with the partial positive charges of the hydrogen regions of water molecules. Eventually, water dissolves all the ions, resulting in a solution with two solutes: sodium and chloride ions.

What is it called when two atoms are put together?

molecule

Hydrophobic substances are made of

mostly nonpolar covalent bonds. Because no regions have partial or full charges, water molecules cannot form hydrogen bonds with hydrophobic molecules.

In cells, the electronegative partners are typically

nitrogen or oxygen.

A covalent bond between two atoms of the same element is always

nonpolar because they are always equally strong. Because carbon and hydrogen have

emergent properties

occur when the combination of two things gives you a new trait that neither single thing alone has. Table salt is a great example.

Electronegativity is a measure

of how "greedy" the atom is with respect to electrons.

What four elements make up 96% of living things?

oxygen(o), carbon (I), hydrogen(H), and nitrogen

How to find number of neutrons?

subtract the number of protons (atomic number) from the mass number

The reversibility of weak bonding creates an advantage:

two molecules can come together, respond to each other in some way, and then separate.

Why do they want a complete set? It is because incomplete electron shells are

unstable and anything unstable that is given a chance to move to a more stable state will do so.

The universal solvent is ____________________ and one solute that can dissolve in it is ______________. Question options: oil, sugar oil, salt water, salt water, oil gasoline, powder

water, salt

The chemical potassium bicarbonate is used in club soda for taste. It is made up of potassium, carbon, hydrogen and oxygen, This is an example of A trace element A vitamin An atom An emergent property A periodic table component

An emergent property

electron shell

An energy level representing the distance of an electron from the nucleus of an atom.

chemical bonds form because

Atoms with incomplete valence shells can interact with each other by sharing or transferring valence electrons so that they both become complete.

An element occurs as a mixture of isotopes like

For example, 99% of carbon atoms have 6 neutrons (12C). Most of the remaining 1% of carbon atoms have 7 neutrons (13C), while the rarest carbon isotope, with 8 neutrons, is 14C. Most isotopes are stable; they do not tend to lose particles. Both 12C and 13C are stable isotopes.

Some bases reduce the___________ directly by accepting hydrogen ions.

H+ concentration. This modifies the concentrations of hydrogen and hydroxide ions.

A simplified way to view this process is to say that a water molecule dissociates into a hydrogen ion and a hydroxide ion:

H2O → H+ + OH-

One difference between hydrophilic (polar) and hydrophobic (non-polar) molecules is Question options: Hydrophilic molecules cannot form hydrogen bonds but hydrophobic molecules can Hydrophilic molecules can separate charges and hydrophobic cannot Hydrophilic molecules contain oxygen but hydrophobic molecules do not Hydrophilic molecules include oils and hydrophobic molecules include water Hydrophilic molecules have don't dissolve in water but hydrophobic molecules do

Hydrophilic molecules can separate charges and hydrophobic cannot

What happens if one atom is really really electronegative?

If two atoms are very unequal in their attraction for valence electrons, the stronger atom strips an electron completely away from the other. This is called ionization

Sodium Chloride is an example of Ionic bond James Bond nonpolar bond hydrogen bond

Ionic bond

Have you noticed that paper towels don't absorb oil very well?

Oils such as vegetable oil are hydrophobic because the dominant bonds, ie., carbon-carbon and carbon-hydrogen, are nonpolar. As a result, they are not sticking to the plant fibers very well.

Radioactive isotopes have many applications in biological research. Like...

Radioactive decay rates can be used to date fossils. Radioactive isotopes can be used to trace atoms through metabolic processes. Radioactive isotopes are also used to diagnose medical disorders. A known quantity of a substance labeled with a radioactive isotope can be injected into the blood, and its rate of excretion in the urine can be measured.

electronegativity

The attraction of an atom for the shared electrons of a covalent bond

valence shell

The chemical behavior of an atom depends mostly on the number of electrons in its outermost shell

a hydrogen ion (H+)

The hydrogen atom leaves its electron behind and floats away as a single proton

Unstable Isotopes

The nuclei of some isotopes are unstable and decay spontaneously, emitting particles and energy. 14C is one of these unstable isotopes, or radioactive isotopes. When 14C decays, one of its neutrons is converted to a proton and an electron. In this process, 14C is converted to 14N, a different element.

hydroxide ion (OH−).

The water molecule that lost the proton

Which of the following is NOT a major component of living systems Nitrogen Hydrogen Titanium Oxygen Carbon

Titanium

True or False: Water has many unusual properties because of the attraction between polar water molecules. The slightly negative regions of one water molecule are attracted to the slightly positive regions of nearby water molecules, forming hydrogen bonds.

True

True or false: Chemical reactions rearrange matter; they do not create or destroy matter.

True

True or false: Each hydrogen bond lasts only a few trillionths of a second, but the molecules continuously form new hydrogen bonds with a succession of partners.

True

True or False: Oxygen is electron greedy.

True. Veeeeery electron greedy. So occasionally, an oxygen atom completely steals the electron from one of its hydrogen atoms, turning it into an ion.

nonpolar covalent

Two atoms of equal strength will share the electrons equally.

isotopes

Two atoms of the same element that differ in the number of neutrons

A trace element

are those atoms required by an organism, but only in minute quantities. Trace elements are common additives to food and water.

The measurement that tells the effective weight of an atom is Question 1 options: metalic weight atomic mass atomic weight mass weight nuclear mass

atomic mass

Covalent bonds can form

between atoms of the same element (forming pure elements) or atoms of different elements (forming compounds).

Hydrogen bonds______, ________, and __-________ with great frequency.

bonds form, break, and re-form

The remaining 4% of an organism' weight consists of?

calcium (Ca), phosphorus (P), potassium (K), sulfur (S), and sodium (Na).

Each water molecule can form hydrogen bonds with as many as six neighbors ten neighbors four neighbors two neighbors

four neighbors

Compounds with a polar covalent bond

have regions of partial negative charge (δ-) near the strongly electronegative atom and regions of partial positive charge (δ+) near the weakly electronegative atom. These partial charges act like the + and -"poles" of a magnet, giving it the name "polar." These partial charges will be very important when we talk about hydrogen bonds. Every polar bond we talk about in this course will either involve oxygen or nitrogen as the highly electronegative atom.

Even large molecules, like proteins, can dissolve in water if they have ionic and polar regions. Things that dissolve in water are called

hydrophilic (water-loving). Hydrophilic substances contain multiple ionic or polar bonds. For example, paper is hydrophilic because plant fibers have lots of polar covalent bonds. However, its giant fiber molecules are too large to dissolve in water. When water molecules form hydrogen bonds with the cellulose fibers of paper, the water actually gets stuck to the fiber! This is why, when you wipe up a spill with a paper towel, the water is pulled into the towel.

Substances that have no affinity for water are

hydrophobic (water-fearing).

In a chemical reaction, all of the atoms of the reactants must be present in the___________.

products.

PET scans rely on Question 2 options: radioactive isotopes atomic mass neutrons carbon dating sodium chloride

radioactive isotopes

The starting molecules in the process are called_______, and final molecules are called________.

reactants, products

To maintain cellular pH values at a constant level, biological fluids have buffers. Buffers...

resist changes in the pH of a solution when H+ or OH− is added to the solution. Buffers accept hydrogen ions from the solution when they are in excess and donate hydrogen ions when they have been depleted. Blood for example is buffered with bicarbonate (similar to baking soda), which resists changes to pH outside of 7.4.

Polar molecules are (soluble/insoluble) in water because they form hydrogen bonds with water.

soluble

A liquid with dissolved substances is called a

solution

A sugar cube in a glass of water dissolves to form a solution of sugar and water. The dissolving agent is the____________, and the substance that is dissolved is the______________. In our example, water is the solvent and sugar is the solute. In biology, water is almost always the solvent.

solvent; solute

When oxygen and hydrogen form water,

the bonds between oxygen and hydrogen are polar covalent because oxygen has a much higher electronegativity than hydrogen.

The pH of a cell is determined by Question options: the size of the cell the amount of sodium in the cell the concentration of H+ (hydrogen ions) in the cell the type of cell (i.e. neuron, red blood cell, kidney cell, etc.) the temperature of the cell

the concentration of H+ (hydrogen ions) in the cell

mass number

the effective weight of an atom. It is the sum of the number of protons and the number of neutrons in the nucleus of an atom. It doesn't include electrons because their mass is so small.

atomic mass

the mass number is an approximation of the total mass of an atom

Isotopes differ in Question 3 options: the number of elements the number of protons the number of electrons the number of neutrons

the number of neutrons

When two atoms share valence electrons Question options: they form a nonpolar interaction they form an acidic solution they form a covalent bond they form a hydrogen bond they have fun

they form a covalent bond

The pH scale is used

to describe how acidic or basic a solution is.

What is the purpose of a buffer (in a biological organism)? Question options: to maintain concentration of ion level bodily fluids to make a cellular temperature constant to make a cellular pH more acidic to maintain a proper cellular pH to make a cellular pH more basic

to maintain a proper cellular pH

The partially positive-charged hydrogen atom is attracted

to regions of full or partial negative charge on molecules, atoms, or even regions of the same large molecule.