Multiple Choice
Which two elements were discovered by Marie and Pierre Curie?
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2. Atoms & Elements
Periodic Table: Representative Elements & Transition Metals
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Which of the following elements is an alkali metal with fewer than 10 protons in its nucleus?
A
Sodium (Na)
B
Potassium (K)
C
Magnesium (Mg)
D
Lithium (Li)
Verified step by step guidance1
Recall that alkali metals are elements in Group 1 of the periodic table. These elements have one electron in their outermost shell and are highly reactive metals.
Identify the atomic numbers (number of protons) of the given elements: Sodium (Na) has 11 protons, Potassium (K) has 19 protons, Magnesium (Mg) has 12 protons, and Lithium (Li) has 3 protons.
Since the problem asks for an alkali metal with fewer than 10 protons, eliminate Sodium, Potassium, and Magnesium because their atomic numbers are greater than 10.
Confirm that Lithium (Li) is an alkali metal (Group 1) and has an atomic number of 3, which is fewer than 10 protons.
Conclude that Lithium (Li) is the correct answer because it meets both criteria: it is an alkali metal and has fewer than 10 protons.
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