EasyChemistryHigh School (9–10)GeneralStructure of the Atom › Electronic Configuration and ValencyStructure of the Atom › Isotopes and IsobarsNumericalBoard Exam
An atom has 19 protons and 20 neutrons. The element is potassium, K.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
An atom has protons and neutrons. The element is potassium, K.
- Find its atomic number and mass number.
- Write its symbol in the form .
- How many electrons does the neutral atom have?
Need a reminder? The key ideaShow
The atomic number is the number of protons, and it decides the element. The mass number is protons plus neutrons, so neutrons . A neutral atom has electrons. An ion has the same nucleus; only the electrons change, by the charge.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) . .
Step 2. (b) : the mass number at the top, the atomic number at the bottom.
Step 3. (c) A neutral atom has as many electrons as protons: .
Answer: (a) , . (b) . (c) electrons.
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