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semester 1 biology exam
Terms in this set (23)
the four most common elements in living organisms are?
which of the following statements regarding matter is false?
all matter exist in a form of compounds.
which of the following statements best describes a compound.
contains two or more different elements in a fixed ratio.
in the equation 2 H2 +O2--->2 H2O
only the H2 and O2 are compounds
which of the following trace elements needed by human is is commonly added to table salt?
in some areas fluoride is added to the water treatment process in order to help?
reduce tooth decay
which of the following particle are found in the nucleus of an atom?
protons and neutrons
what is the atomic mass of an atom that has 6 protons, 6 neutron, and 6 electrons?
the sodium atom contains 11 electron, 11 protons, and 12 neutrons. what is the atomic number of an atom?
an uncharged boron atom has an atomic mass of 11. how many electrons does boron have?
which of the following best describes the atomic number of an atom?
the number of protons in the atom
typically nitrogen atoms are composed of electrons, protons, and neutrons. an isotope of nitrogen could ?
have more neutrons than the usual nitrogen atom
a radioactive isotope is an isotope that?
which of the following about radioactive isotopes is true?
the energy emitted can break chemical bonds and cause molecular damage.
can be used in conjunction with pet scans to diagnose diseases
A_____forms when two atoms share electrons
a hydrogen atom has one electron. how many covalent bonds can hydrogen form?
What is the fundamental difference between covalent and ionic bonds?
in covalent bonds they share electrons, in ionic bonds one partner accepts electrons from the other.
which of the following statements regarding the the oxygen atom of a water molecule is true?
oxygen is more electronegative than the hydrogen atoms.
in water hydrogen and oxygen are held together by what bond?
polar covalent bond
The hydrogen atoms of water are bonded to the oxygen atom by_____ bonds, whereas neighboring water molecule are held together by _____ bonds
polar covalent hydrogen
water molecule stick other water molecules because
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?
some chemical reactions create electrons; others destroy them
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