Atomic structure and isotopes: แบบฝึกหัด

What is the correct electronic configuration for an atom of sodium, which has an atomic number of 11?

An unknown element X has the electronic configuration 2.8.8.2. Which of the following statements correctly identifies its position in the periodic table and its most likely ionic formula when it reacts with nitrate ions, \(NO_{3}^{-}\)?

Substance Y has a melting point of \(801^{\circ}\text{C}\) and a boiling point of \(1413^{\circ}\text{C}\).
It conducts electricity when molten but not when solid.
Explain this observation in terms of the particles present in substance Y.

Which subatomic particle has a relative mass of \(\frac{1}{1836}\) (often approximated as \(\frac{1}{1840}\) or almost zero) and a relative charge of \(-1\)?

Two substances, A and B, are tested.
- Substance A has a melting point of 1085 °C and conducts electricity as a solid.
- Substance B has a melting point of 801 °C and conducts electricity only when molten or in solution.

Identify the types of bonding and structure for A and B.

An atom of carbon has a mass number of 12 and an atomic number of 6. Calculate the number of neutrons present in the nucleus of this atom.

A sample of magnesium contains two isotopes: \( ^{24}\text{Mg} \) with an abundance of \( 75\% \) and \( ^{26}\text{Mg} \) with an abundance of \( 25\% \).
Calculate the relative atomic mass of this sample of magnesium.

A sample of magnesium is reacted with excess dilute hydrochloric acid in an open flask.
State the law of conservation of mass and explain why the mass of the flask and its contents appears to decrease during this specific reaction.

(a) The Dalton model of the atom has changed over time as subatomic particles were discovered. State the names of the three subatomic particles that make up an atom. (1 point)

(b) Describe the structure of an atom in terms of the position of these subatomic particles. (2 points)

(c) Explain why an atom has no overall charge, referring to the numbers and relative charges of the subatomic particles. (2 points)