Chapter 2: The Context of Life Pt. 1

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The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. Upon ionization, what would you expect the charge on the sulfate ion to be?

-2

glucose

C6H12O6

Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).

three fewer neutrons

A neutral atom of chlorine has an atomic number of 17. It has _____ electrons in its third shell.

7

An element has 8 protons, 9 neutrons, and 8 electrons. Its atomic number and atomic mass, respectively, are

8 and 17

A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. The respective number of neutrons, protons, and electrons that this carbon isotope has is

8, 6, and 6

Which of the following four statements, if any, is true regarding essential elements and living organisms?

Although all forms of life require iron, other elements are required only by certain species.

Consider this statement: Oxygen is not a greenhouse gas; therefore, gases containing oxygen, such as ozone, nitrous oxide, and carbon dioxide, are not greenhouse gases either. Which is a valid response to this statement?

False. Compounds can have emergent properties that are very different from the elements that form them.

Consider this statement: Concentrations of trace elements in an environment above what is required by organisms generally has no effect on those organisms. Which is a valid response to this statement?

False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.

Consider a hypothetical atom with an atomic number of 4 and a net charge of +1. How many neutrons does this ion have?

The answer cannot be determined from the information provided.

Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?

The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge.

These elements make up 96% of living matter.

The elements carbon, hydrogen, nitrogen, and oxygen make up 20-25% of living mass.

What describes a reversible reaction that has reached chemical equilibrium?

The rate of the reverse reaction equals the rate of the forward reaction

Which of the following statements is true about chemical reactions?

They involve the making and breaking of chemical bonds

When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?

a covalent bond

The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?

an atom with 20 protons, 21 neutrons, and 20 electrons

Isotopes of an element will always differ in

atomic mass

Ionic bonds form as a result of

attraction between ions that have opposite charges

Gaining or losing a proton would cause the atom to

become a different element.

a trace element

copper

number of protons plus the number of neutrons

determines an atom's mass number

An atom that normally has _____ in its outer shell would not tend to form chemical bonds with other atoms.

eight electrons

negligible mass

electron

The number of protons in an uncharged atom

equals the number of electrons

Atoms with the same number of electrons in their valence shells

exhibit similar chemical behavior or reactivity.

Covalent bonds

formed between atoms that share one or more pairs of valence electrons.

For most atoms, a stable configuration of electrons is attained when the atom

has eight electrons in its outermost shell

These four elements make up about 96% of living matter.

hydrogen, oxygen, nitrogen, and carbon.

What are the four most abundant elements found in living systems?

hydrogen, oxygen, nitrogen, and carbon. These four elements make up about 96% of living matter.

A hydrogen bond

is a weak chemical bond

When the proton number and electron number are unequal, the atom or molecule

is an ion

the neutrons determine the

isotope

Which of the following molecules has the shape of a completed tetrahedron?

methane (CH4)

subatomic particles has appreciable mass and lacks a charge

neutron

The chemical characteristics or reactivity of an element depend mostly on the

number of electrons in its outermost shell

A covalent bond is likely to be polar if

one of the atoms sharing electrons is much more electronegative

Hydrogen bonds occur when

partial opposite charges on molecules come close enough to attract each other

The atomic number is the number of

protons

Isotopes of an element have the same number of

protons but different numbers of neutrons.

the atomic number refers to number of

protons in an atom

An uncharged atom of nitrogen (atomic number = 7) has

seven protons and seven electrons

Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?

the molecule's shape

Radioactive isotopes are useful in scientific research because

they can be used as tracers to follow particular atoms and molecules through metabolic pathways

An atom with a complete valence shell is

unreactive

Attraction resulting from the motion of electrons describes

van der Waals interactions.


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