All 10 questions and answers
Try each question before you open the answer. Recalling first, then checking, is what makes a quiz stick (the testing effect).
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What does an element's atomic number tell you?
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The number of protons in its nucleus. The atomic number is the proton count, and it defines the element. Protons plus neutrons is the mass number.
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Carbon has atomic number 6. How many neutrons does carbon-14 have?
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8. The 14 is the mass number, protons plus neutrons. 14 minus 6 protons leaves 8 neutrons.
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What is different between two isotopes of the same element?
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The number of neutrons. Isotopes have the same number of protons, so they are the same element, but different numbers of neutrons and therefore different masses.
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Which particle in the atom has no electric charge?
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The neutron. Protons are positive, electrons negative, neutrons neutral. The nucleus as a whole is positive because it contains the protons.
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Why do elements in the same group of the periodic table behave similarly?
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They have the same number of valence electrons. Chemical behavior depends mostly on the outer (valence) electrons, and elements in one group share the same outer arrangement.
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Why are noble gases like neon and argon so unreactive?
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Their outer electron shell is full. A full valence shell is a stable arrangement, so noble gases have little tendency to gain, lose or share electrons.
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An atom gains two electrons. What does it become?
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A negative ion with a 2- charge. Electrons are negative, so gaining two gives a charge of 2-. The proton count, and so the element, does not change. Oxygen forming O2- is the classic example.
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How does atomic radius change from left to right across a period?
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It generally decreases. Across a period, protons are added to the nucleus while electrons fill the same shell. The stronger pull draws the electrons closer, so atoms get smaller.
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Which of these elements is an alkali metal?
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Sodium. Alkali metals are group 1: lithium, sodium, potassium and so on. Calcium is an alkaline earth metal (group 2), chlorine a halogen, neon a noble gas.
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Where is almost all of an atom's mass concentrated?
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In the nucleus. Protons and neutrons are each about 1,800 times heavier than an electron. Rutherford's gold foil experiment showed they sit in a tiny, dense nucleus.
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