Chapter 2 Biology Study Guide

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nucleus
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atom’s central core.
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proton
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positively charged, found in the atomic nucleus
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neutron
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no electrical charge, found in the atomic nucleus
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electron
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negatively charged, surround the nucleus in a “cloud” ; orbit the nucleus Can only have 2 electron charges on shell. – orbit the nucleus of an atom in specific electron shells. – number of ___ in the outermost shell determines the chemical properties of an atom.
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energy levels
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represented by electron shells
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potential energy
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energy that matter possesses because of its location or structure
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energy
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the capacity to cause change
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isotopes
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alternate mass forms of an element. they have the same number of protons and electrons. But they have a different number of neutrons
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atomic number
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number of protons of an element
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mass number
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sum of protons + neutrons in nucleus of an atom.
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atomic weight
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valence shell
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The outermost shell
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polar covalent bond
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atoms have differing electronegativities; share the electrons unequally. Example : H2O: O – / + H + H
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nonpolar covalent bond
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atoms have a similar electronegativities; share the electron equally. Example Oxygen gas (O2): O=O
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essential elements
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include carbon, hydrogen, oxygen, and nitrogen. Make up of 96% of living matter.
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ionic bond
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an attraction between anions and cations. Be able to draw example.
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hydrogen bond
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froms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. Be able to draw example.
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covalent bond
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the sharing of a pair of valence electrons. Forms when two atoms share one or more pairs of outer-shell electrons. Be able to draw example. MAKE A TRIANGLE SHAPE Example: H²O: O-H | H
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single bond
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sharing of one pair of valence electrons H²: H-H two hydrogen atoms can form a ____.
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double bond
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sharing of two pairs of valence electrons O²: O=O two oxygen atoms share two pair of electrons to form a ___.
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ion
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atoms with more or fewer electrons than usual; charged atoms.
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cation
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positively charged ions
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anion
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negatively charged ions
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element
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consists of a certain kind of atom that is different from those of other elements.
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molecule
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consists of two or more atoms held together by covalent bonds.
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compound
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a substance consisting of two or more elements combined in a fixed ration. Has characteristics different from those of its elements.
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valence electrons
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those in the outermost, or valence shell. determine the chemical behavior of an atom.
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electronegative
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the attraction of a particular kind of atom for the electrons in a covalent bond. the more ____ an atom, the more strongly it pulls shared electrons toward itself.
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What is the difference between an element and a compound
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Elements and compounds are pure chemical substances found in nature. The difference between an element and a compound is that an element is a substance made of same type of atoms, whereas a compound is made of different elements in definite proportions.
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Describe the structure of an atom
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smalled unit of matter that still retains the properties of an element. Composed of even smaller parts called subatomic particles.
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Define and distinguish among atomic number, mass number, and valence shell
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The atomic number is the number of protons, which is located on top of the element symbol. The mass number is the number of protons+ neurons. Located below the element symbol. The valence shell is the outer most shell. It determines the chemical behavior of an atom.
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Given the atomic number and atomic weight of an atom, determine the number of neutrons
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Number of Neutrons = Mass Number – Atomic Number
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How does an isotope differ from a normal atom?
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Explain how electron configuration influences the chemical behavior of an atom.
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Explain the differences between non polar covalent, polar covalent and ionic bonds.
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In a nonpolar covalent bond, the atoms have similar electronegativities. They share the electron equally. example: O2: O=O In a polar covalent bond the atoms have differing electronegativities; share the electrons unequally.
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Describe the formation of a hydrogen bond and explain how it differs from a covalent or ionic bond.
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How does an ionic bond differs from a covalent bond?
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From the number of electrons in an atom, predict how many bonds an atom might form
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How does electronegativity influence the formation of chemical bonds?
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