Question

which of the following is true when discussing the structure of the atom: *
the nucleus is large and empty compared to the rest of the atom
the nucleus is very small and tightly/densely packed with protons and neutrons
the electron cloud is very empty and only has a few neutrons in it

the mass of an atom depends on which of the following:
protons only
electrons only
protons and neutrons
protons and electrons

which of the following is true when comparing protons and electrons: *
electrons have a positive charge and protons have a negative charge
protons have a positive charge and electrons have a negative charge
protons and electrons both have a positive charge

Explanation:

• First question: The nucleus is very small (about \(10^{-15}\) m in radius) compared to the atom (about \(10^{-10}\) m in radius) and is densely packed with protons and neutrons. Electrons are in the electron - cloud and neutrons are in the nucleus.
• Second question: Protons (\(m_p\approx1.6726\times 10^{-27}\) kg) and neutrons (\(m_n\approx1.6749\times 10^{-27}\) kg) have significant mass, while electrons (\(m_e\approx9.1094\times 10^{-31}\) kg) have negligible mass compared to protons and neutrons. So the mass of an atom depends on protons and neutrons.
• Third question: By definition, protons have a positive charge (\(+e\), where \(e = 1.6\times10^{-19}\) C) and electrons have a negative charge (\(-e\)).

Answer:

• First question: The nucleus is very small and tightly/densely packed with protons and neutrons.
• Second question: protons and neutrons.
• Third question: protons have a positive charge and electrons have a negative charge.