The four most common elements in living organisms are?
What is the atomic mass of an atom that has 6 protons, 6 neutrons,and 6 electrons?
An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many electrons does boron have?
The sodium atom contains 11 electrons, 11 protons, and 12 neutrons. what is the mass number of sodium?
Which of the following best describes the atomic number of an atom?
-the number of electrons in the atom
-the number of neutrons in the atom
-the number of protons,electrons,and neutrons in the atom
-the number of protons in the atom
the number of protons in the atom
a radioactive isotope is an isotope that
-has the same atomic mass but a different atomic number than the common variant of the element
-has more protons than the common variant of the element
typically, nitrogen atoms are composed of electrons,protons,and neutrons. An isotope of nitrogen could
-have more protons than the usual nitrogen atom
-be positively charged
-be negatively charged
-have more neutrons than the usual nitrogen atom
has more neutrons than the nitrogen atom
which of the following statements about radioactive isotopes is true?
-radioactive elements are natural and therefore not harmful
-the energy emitted by radioactive isotopes can break chemical bonds and damage in cells
-when given a choice between radioactive and nonradioactive isotopes of the same atom,living cells are more likely to incorporate the radioactive isotopes into their scructures
-the nuclei of radioactive isotopes are usually stable but the atoms tend to lose electrons
the energy emitted by radioactive isotopes can break chemical bonds and cause molecular damage in cells
which of the following is a trace element in the human body?
when full, the innermost electron shell of argon contains____________ electrons, and the outermost shell contains____________electrons.
what happens to an atom if the electrons in the outer shell are altered?
-the atom disintegrates
-the properties of the atom change
-the atoms characteristics change and it becomes a different element
-the atom becomes radioactive
the properties of the atom change
A/an____________forms when two atoms share electrons.
A hydrogen atom has one electron. How many covalent bonds can hydrogen form?
Table salt is formed when?
-a hydrogen bond forms between sodium and chlorine
-sodium and chlorine share electrons to form a bond
-sodium donates its single outer electron to chlorine
-chlorine gives an electron to sodium
sodium donates its single outer electron to chlorine
the body uses atoms in different ways to accomplish different task. For example, one portion of the bodys calcium supply strengthens bones, whereas another portion combines with proteins to stimulate blood clotting after tissue injury. Which of the following statements provides the most logical chemical explanation of calciums ability to perform such different functions?
-the bone contains calcium salts, which are less reactive than the calcium ions found in the blood
-the calcium in blood is a more reactive form of the atom and therefore has fewer protons than the calcium in bone
-the calcium in blood has a lighter atomic mass than the calcium in bone and is a more reactive form.
The bone contains calcium salts, which are less reactive than the calcium ions found in the blood.`
medicines are often administered in pill form. In many cases, the active ingredient of the pill (the drug) is joined to another substance by_______. This forms a/an_____, which is stable in the dry environment of a pill bottle but dissociates under the wet conditions of the digestive system to release the drug to the body.
What is the fundamental difference between covalent and ionic bonding?
-covalent bonding involves only the outermost electron shell;ionic bonding also involves the next electron shell inside the outermost shell
-in covalent bonding, both partners end up with filled outer electron shells; in ionic bonding, one partner does and the other does not
-in a covalent bond, the parters share a pair of electrons; in an ionic bond, one partner accepts electrons from the other
in a covalent bond, the parters share a pair of electrons; in an ionic bond, one partner accepts electrons from the other
which of the following statements regarding the oxygen of a water molecule is true?
-oxygen is attracted to the negatively charged atoms of other molecules
-oxygen is more positively charged than the hydrogen atoms
-oxygen is more electronegative than the hydrogen atoms
-oxygen attracts electrons less strongly than the hydrogen atoms
oxygen is more electronegative than the hydrogen atoms
in a water molecule, hydrogen and oxygen are held together by a ____________ bond.
Which of the following statement regarding matter is false?
-all matter has mad
-all matter exist in the form of compounds
-all life is composed of matter
-all matter is composed of elements
all matter exist in the form of compounds
A single water molecule (H-0-H) is held together by
-two polar covalent bonds
-a double covalent bond
-a single covalent bond
two polar covalent bonds
the hydrogen atoms of a water molecule are bonded to the oxygen atom by___________bonds, whereas neighboring water molecules are held together by_________bonds.
-hydrogen ;polar covalent
-polar covalent; hydrogen
-polar covalent; ionic
_________are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.
-polar covalent bonds
water molecules stick to other water molecules because?
-covalent bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of the water molecules
-water molecules are neutral, and neutral molecules are attracted to each other
-hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules
-the oxygen atoms of adjacent water molecules are attracted to one another
hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules
which of the following statements regarding chemical reactions is false?
-the reactants contain the same number of atoms as the products
-chemical reactions involve the making and breaking of chemical bonds
-some chemical reactions create electrons;others destroy them
-although the atoms of a reactions reactants and products are identical to each other, their molecular formulas differ
some chemical reactions create electrons;others destroy them
In the equation 2H2+2H20, the H2 molecules are___________and the H2O molecules are____________
In plants, the process of photosynthesis produces glucose (C6H12O6) and oxygen from carbon dioxide and water. Which of the following statements about photosynthesis is true?
-more atoms are present at the beginning than at the end
-all the carbon atoms from the carbon dioxide atoms are found in glucose
-water is synthesized by the plant from H2 and O2
-More carbon dioxide is released from the plant than is absorbed
all the carbon atoms from the carbon dioxide atoms are found in glucose
the tendency of water molecules to stick together is referred to as?
Waters surface tension and heat storage capacity are accounted for by its?
the temperature of evaporation is much higher for water than for alcohol. without knowing more about the chemistry of alcohol,which of the following is the most logical chemical explanation for this phenomenon?
-alcohol molecules are more cohesive than water molecules.this means that as alcohol molecules evaporate. they pull other alcohol molecules into the air with them
-ionic bonds form between alcohol molecules. these are the weakest type of bond and are easier to break than the hydrogen bonds between water molecules
-fewer hydrogen bonds form between alcohol molecules. as a result, less heat is needed for alcohol molecules to break away from solution and enter the air
fewer hydrogen bonds form between alcohol molecules. as a result, less heat is needed for alcohol molecules to break away from solution and enter the air
which of the following statements best describes a compound?
-a compound is a solution
-a compound is a pure element
-a compound is exemplified by sodium
-a compound contains two or more different elements in a fixed ratio
a compound contains two or more different elements in a fixed ratio
as ice melts,
-heat is released
-the water becomes less dense
-hydrogen bonds are broken
-water molecules become less tightly packed
hydrogen bonds are broken
which of the following statements about water is false?
-ice is more dense than liquid water
-if ice sank, the ocean would eventually freeze solid
-floating ice on a pont insulates the liquid water below, slowing is the rate of freezing
-water naturally exist in all three physical states on earth
ice is more dense than liquid water
you've made a hot drink by dissolving a teaspoon of instant coffee and a teaspoon of sugar
in a cup of hot water. which of the following statements is true?
-youve just prepared an aqueous solution
-the instant coffee and sugar are solvents
-the instant coffee and sugar dissolve because they have no charged regions to repel the partial positive and partial negative regions of water molecules
-the water is the solute portion of the drink
you've just prepared an aqueous solution
which of the following is dependent on the ability of water molecules to form hydrogen bonds with other molecules besides water?
-the milder temperatures of costal regions compared to inland areas
-the evaporative cooling of skin surfaces
-the ability of certain insects to walk on the surface of water
-the universality of water as a solvent
the universality of water as a solvent
clots in our blood can lead to a heart attack or stroke by blocking blood flow. If a clot were made up of a mass of proteins, what changed in the proteins to cause them to form the clot?
-the blood became saturated with proteins
-the proteins were no longer soluble in the blood
-the proteins became more soluble in the blood
-the proteins became more polar
the proteins were no longer soluble in the blood
A solution with a pH of 7 is?
Compared to a solution of pH3, a solution of pH 1 is?
-100 times more basic
-100 times more acidic
-10 times more basic
-10 times more acidic
100 times more acidic
which of the following statements about pH is true?
-an increase in hydrogen ion concentration means a decrease in pH scale units
-basic pH levels are less than 7
-a single unit change on the pH scale is equivalent to a 1% change in hydrogen ion concentration
-the pH scale is a measure of oxygen ion concentration
an increase in hydrogen ion concentration means a decrease in pH scale units
Household ammonia has a pH of 12; household bleach has a pH of 13. Which of the following statements about these substances is true?
-the ammonia has 10 times as many OH- ions as the bleach
-both of these substances are strong acids
-the ammonia has 10 times as many H+ ions as the bleach
-a solution that could buffer the bleach and ammonia would remove excess OH- ions
the ammonia has 10 times as many H+ ions as the bleach
in the equation 2 H2+o2----> 2 H20,
-only H20 is a compound
-H202,and H20 are all elements
-only H2 and O2 are compounds
-H2,O2,and H20 are all compounds
only H20 is a compound
-is a base that is used to offset overtly acidic conditions in the body
-donates H+ ions when conditions become too basic and accepts H+ ions when conditions become too acidic
-donates OH- ions when conditions become too basic and accepts OH- ions when conditions become too acidic
-is an acid that is used to offset overly basic conditions in the body
donates H+ ions when conditions become too basic and accepts H+ ions when conditions become too acidic
Silicon is an element that is found directly underneath carbon in the periodic table. How many electrons are in the valence shell of a silicon atom?
Which of the following trace elements needed by humans is commonly added to table salt?
in some areas, fluoride is added during the municipal water treatment process in order to help
-prevent the development of mental retardation
-reduce tooth decay
-prevent the growth of bacteria
reduce tooth decay
which of the following particles are found in the nucleus of an atom?
-protons and electrons
-protons and neutrons
protons and neutrons
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