Section 1
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Chemical reactions
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Section 1
(50 cards)
Chemical reactions
- The making and breaking of chemical bonds, leading to changes in the composition of matter. - Matter is neither created nor destroyed, only rearranged. - Reactions are reversible.
Valence Shell
- The outermost electron shell. - An atom with a completed valence shell is unreactive because it is stable (inert).
Toxic Elements
- Some naturally occurring elements are toxic to organisms. - Some species have adapted to environments containing elements that are usually toxic. - Ex. Sunflowers can absorb lead, zinc and other heavy metals in concentrations that would kill other organisms.
Compound
- A substance consisting of two or more different elements combined in a fixed ratio - Has chemical and physical characteristics different from those of its elements - Ex. Water (H20) is a compound that has a 2:1 ratio
Reactants
- Starting materials in a chemical reaction
Hydrogen bonds
- Partial positive charge of a hydrogen atom that is covalently bonded to an electronegative atom allows the hydrogen to be attracted to a different electronegative atom nearby. - A hydrogen bond is the nonequivalent attraction between a hydrogen and an electronegative atom.
Molecule
- Composed of 2 or more atoms held together by covalent bonds.
Water's polarity
- Unequal sharing of electrons and water's V- like shape make it a polar molecule. - The oxygen region has a partial negative charge. - Each hydrogen has a partial positive charge - Because of this, the hydrogen of one molecule is attracted to the oxygen of another molecule, forming a hydrogen bond.
Adhesion
- The clinging of one substance to another.
Advantages of weak chemical bonds
- Two molecules can adhere temporarily by weak bonds. - Two molecules can come together, respond to one another in some way and then separate.
Molecular Shape
- Determines how biological molecules recognize and respond to one another with specific. - Complementary molecules bind to each other. - Ex. Because opiates have similar shapes to endorphins, they bind to endorphin receptors in the brain.
Double bond
- 2 shared pairs of valence electrons. - Represented by 2 lines
Potential Energy
- Energy that matter possesses because of its location or structure - Matter has a natural tendency to move to the lowest possible state of potential energy.
Ionic compounds/salts
- Compounds formed by ionic bonds. - Does not consist of molecules, only elements.
Atom
- The smallest unit of matter that still retains the properties of an element. - Each element consists of a certain type of atom that is different from the atoms of any other element. - Most empty space
Essential Elements
- Elements that an organism needs to live a healthy life and reproduce
Ion
- A charged atom (or molecule). - Electrons have either been lost or gained.
Anion
- Negatively charged atom. - An electron has been gained.
Proton
- Charge: positive - Location: nucleus - Mass: 1 dalton
Products
- The elements or compounds produced by a chemical reaction.
Polar covalent bond
- Bond where an atom is bonded to a more electronegative atom. - Electrons are not shared equally.
Chemical Bonds
- Bonds between atoms when they either share or transfer valence electrons. - The strongest kinds of chemical bonds are covalent and ionic bonds. - When bonds form, they make fill the atoms valence shell
Single Bond
- A pair of shared electrons. - Represented by a single line
Neutron
- Charge: electrically neutral - Location: nucleus - Mass: 1 dalton
Subatomic particles
- Compose atoms. - Three relevant kinds: neutrons, protons and elections
Electronegativity
- The attraction of a particular atom for the electrons of a covalent bond. - The more electronegative an atom is, the more strongly it pulls shared electrons towards itself.
Ionic Bond
- Formed by the attraction of cations and anions. - Electrons are transfered. - Environment affects the strength of ionic bonds. - Dry salt crystal- bonds are very strong. - Salt crystal dissolved in water- bonds are waker because each ion is partially shielded by its interactions with water molecules.
Mass Number
- Sum of the protons and neutrons in the nucleus of an atom.
Cohesion of Water
- Result of the hydrogen bonds that hold water together. - Contributes to the transport of water & dissolved nutrients.
Atomic Number
- Number of protons. - All atoms of a particular element have the same atomic number. - If an atom is neutral, the # of protons= # electrons
Isotope
- Different atomic forms of the same element. - Same number of protons, different number of neutrons. - Behave identically in chemical reactions.
Atomic Mass
- An approximation of the total mass of an atom. - Same number as the Mass Number.
Trace Elements
- Elements that are required by an organism in small quantities. - Ex. in vertebrates iodine is an essential ingredient of a hormone produced by the thyroid gland.
Valence Electrons
- The outermost electrons. - Chemical behavior depends mostly on valence electrons. - Atoms with the same number of electrons in their valence shells exhibit similar chemical behavior.
Chemical equilibrium
- The point at which the reactions offset one another exactly. - This is dynamic: reactions still occur, but with no effect on the concentrations of reactants and products. - Concentrations are stabilized at a ratio.
Valence
- Bonding capacity of an atom - Usually equals the number of electrons required to complete the atom;s outermost (valence shell)
Cation
- Positively charged atom. - An electron has been lost.
Element
- A substance that cannot be broken down to other substances by chemical reactions - 92 naturally occurring elements
Nonpolar covalent bond
- A bond where the electrons are shared equally because the two atoms have the same electronegativity. - Ex. H2 is nonpolar
Radioactive Isotope
- Isotope where the nucleus decays spontaneously giving off particles and energy. - Decay will lead to a change in the number of protons, and the atom transforms to an atom of a different element.
Van deer Walls Interactions
- Individually weak bonds that occur only when atoms and molecules are very close together. - Ex. Geckos can climb up walls because their toes have tiny hairs and there are van der Waals interactions between the hair tip molecules and the molecules of the wall's surface. Because they are so numerous they can support the Gecko's body.
Electron Shells
- Places of high probability of finding an electron. - First shell- lowest potential energy, and so forth - An electron can change its shell by absorbing/ loosing energy. - 1st shell holds 2 electrons, 2nd shell holds 8 electrons
Matter
- Anything that takes up space and has mass - Composes organisms - Made up of elements
Energy
- The capacity to cause change by doing work.
Electron Distribution & Chemical Properties
- The chemical behavior of an atom is determined by the distribution of electrons in the atom's electron shells.
Electron
- Charge: negative - Location: orbits around the nucleus - Mass: so small that electrons are insignificant when computing the total mass of an atom
Atomic Nucleus
- The center of an atom - Has a positive charge due to the protons inside of it
Electrons & Potential Energy
- The electrons of an atom have potential energy because of how they are arranged in relation to the nucleus. - Because negative electrons attract to the positive nucleus, it takes work to move an electron father away from the nucleus. - The farther away an electron is from the nucleus, the greater its potential energy. - An electron's potential energy is determined by its energy level.
Surface tension
- A measure of how difficult it is to stretch or break the surface of a liquid. - Hydrogen bonds in water give it a very high surface tension.
Covalent Bond
- The sharing of a pair of valence electrons by two atoms.
Section 2
(29 cards)