Molecule: two or more different or same atoms chemically bonded together. A mixture contains two or more substances, that are not chemically bonded together. A compound is a pure substance, while a mixture is not.
Answer: With atomic number 20, calcium atoms have 20 positive protons, and the ion has only 18 electrons, which means the net charge is +2. Calcium ions are essential for muscle contractions, nerve impulses, and bone maintenance.
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Answer:
alkali metals
Explanation:
they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
