Question

a potassium atom (atomic number 19) loses an electron while forming a bond with another atom. which best describes the potassium ion that forms?
it is a negative ion that has one less valence electron than a neutral potassium atom.
it is a negative ion that has one more valence electron than a neutral potassium atom.
it is a positive ion that has one less valence electron than a neutral potassium atom.
it is a positive ion that has one more valence electron than a neutral potassium atom.
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Explanation:

1. Recall ion formation: Atoms lose electrons to form positive ions (cations) and gain electrons to form negative ions (anions).
2. Analyze potassium: A potassium atom (K) has 19 protons and 19 electrons (neutral). When it loses an electron, it has 18 electrons but still 19 protons. Since protons (+) outnumber electrons (-), it becomes a positive ion ($\text{K}^+$).
3. Valence electrons: A neutral K atom has 1 valence electron (group 1 metal). Losing that 1 electron means the ion has 0 valence electrons (1 less than neutral K).
4. Evaluate options:

• First two options say "negative ion" – incorrect (losing e⁻ gives positive ion).
• Fourth option says "one more valence electron" – incorrect (losing e⁻ decreases valence electrons).
• Third option: "positive ion" (correct, lost e⁻) and "one less valence electron" (correct, lost its 1 valence e⁻).

Answer:

It is a positive ion that has one less valence electron than a neutral potassium atom. (The corresponding option from the choices, e.g., if it's the third option in the list, state the option text as above.)