chapter 2 Flashcards
Organisms are chemical machines. What is chemistry the science of?
Chemistry is the science of change.
What is any substance in the universe that has mass and occupies space is comprised of ?
Any substance in the universe that has mass and occupies space is comprised of matter. All matter is made up of atoms.
All atoms have the same structure. What is it?
At the core is a dense nucleus comprised of two subatomic particles
protons (positively charged) 1 mass unit
neutrons (no associated charge) 1 mass unit
Orbiting the nucleus is another cloud of subatomic particles, electrons, which are negatively charged and have low mass unit.
atomic number formula
Atomic number = number of electrons = number of protons
atomic mass/mass number formula
Atomic mass/mass number=number of protons and number of neutrons
define atomic number
The number of protons in the nucleus.
Atoms with the same atomic number exhibit the same chemical properties and are considered to belong to the same element
define atomic mass
The number of protons plus neutrons in the nucleus.
Electrons have negligible mass.
Which subatomic particle determines the chemical behavior of atoms?
Electrons determine the chemical behavior of atoms, Electrons have energy of position, called potential energy
What are orbitals?
electron shells, of an atom, are actually complex, three-dimensional volumes of space called orbitals.
How many electrons can each level of orbital hold?
First shell can only hold 2, Second shell can only hold 8, Third shell can hold 8, and so on. Atoms that have incomplete electron orbitals tend to be more reactive
What happens when electrons move to different energy levels?
As electrons move to a lower energy level, closer to the nucleus, energy is released.
Moving electrons to energy levels farther out from the nucleus requires energy.
What are ions?
atoms that have gained or lost one or more electrons
What are isotopes?
atoms that have the same number of protons but different numbers of neutrons. Most elements in nature exist as mixtures of different isotopes.
What is radioactive decay?
Some isotopes are unstable and break up into particles with lower atomic numbers.
What are the uses of radioactive isotopes?
Dating fossils and Medical procedures. Short-lived isotopes decay rapidly and do not harm the body and can be used as tracers in medical diagnoses and studies
What is a molecule?
a group of atoms held together by energy in the form of a chemical bond.
What are the three principal types of chemical bonds?
ionic, covalent, hydrogen
What does the “co” in covalent mean?
“Co” means share
What are Van der Waals forces?
Van der Waals forces are a kind of weak chemical attraction (not a bond) that come into play when atoms are very close to each other
What is an ionic bond?
In an ionic bond, the metal will lose it’s end of the rope to the nonmetal. The “loser” is the metal and the “winner” is the nonmetal. The metal loses electrons to a nonmetal.
Is Ice less dense than water?
Yes, ice is less dense than water.
What is an example of an ionic bond?
NaCl is an example of an this bond.
Molecules formed by an ionic bond are often as stable as?
Molecules comprised of these bonds are often stable as crystals. Crystals are defined as a solid state in which atoms are packed together tightly. The distinguishing feature of crystals is that their solid form is symmetrical on all sides.
Does crystal formation occur in covalent bonds?
Yes, electrons jump out of the shell in the ionic bond.
When do covalent bonds form?
Covalent bonds is when the electronegativity of two bonding atoms is very similar, neither atom wins the “tug of war” and the electrons are shared equally. Covalent bonds form between two atoms when they share electrons
What is the difference between covalent and ionic bonds?
Covalent bonds are stronger than ionic bonds and are directional
What is an example of a covalent bond?
H2 (Hydrogen gas)
What are the two types of covalent bonds?
Polar (one is bigger) and Nonpolar (same size)
How are polar covalent bonds formed?
Some atoms may be better at attracting the shared electrons of a covalent bond. This creates tiny partial negative and positive charges within the molecule, now called a polar molecule (there is a great electronegativity difference). Polar covalent bonds form when the shared electrons of a covalent bond spend more time in the vicinity of a particular atom.
What are hydrogen bonds?
weak electrical attractions between the positive end of one polar molecule and the negative end of another. Water molecules can also form hydrogen bonds
What is the difference in strength between bonds?
Covalent>Ionic>Hydrogen (CIH)
What are the 7 unique properties of water?
Water is essential for life, a polar molecule, heat storage (water temperature changes slowly and holds temperature well), ice formation (water becomes less dense as it freezes because hydrogen bonds hold water molecules farther apart), High Heat of Vaporization (water requires tremendous energy to vaporize because hydrogen bonds must be broken), Water molecules are attracted to other polar molecules, and High polarity (In solution, water molecules tend to form the maximum number of hydrogen bonds.)
What is adhesion?
when polar molecules other than water stick to a water molecule
What is cohesion?
when one water molecule is attracted to another water molecule
What does hydrophilic mean?
molecules are attracted to water and dissolve easily in it. These molecules are also polar and can form hydrogen bonds.
What does hydrophobic mean?
molecules are repelled by water and do not dissolve. These molecules are nonpolar and do not form hydrogen bonds.
What is pH?
The amount of ionized hydrogen from water in a solution can be measured as pH.
The pH scale is logarithmic. What does this mean?
a pH scale difference of 1 unit actually represents a 10-fold change in hydrogen ion concentration. 1 pH unit=10 fold change in H concentration number
What is the range of acidic and basic pH?
Basic>7
Neutral=7
Acidic<7
