<u>Answer</u>
1/4
<u>Explanation</u>
half life = 15 years
decay period = 30 years
The number of half-lives = 30 ÷ 15
= 2 half lives
1 ⇒(<em>after 1st half life</em>) ⇒ 1/2 ⇒ (<em>after 2nd half life</em>) ⇒ 1/4
The fraction that remained is 1/4.
The <span>Atomic theory that states that atoms have three fundamental parts, and that electrons orbit the nucleus is the kinetic molecular theory of gases.</span>
It depends on the electricity passed with cold water or hot water it also depends on the structure of the object in gas the current flows faster than solid or liquid
The number of protons for an atom with 20 neutrons and 20 electrons will be 20.
<h3>
What is an atom ?</h3>
An atom is the smallest particle of an element. It consist of proton, neutron and electron.
To determine the number of protons and also identify the correct symbol for an atom with 20 neutrons and 20 electrons, we must first acknowledge the following facts
- Atom in a neutral state, the number of protons must be equal to number of electrons.
- Atom in a nuclear stable state, number of protons must be equal to the number of neutrons
Therefore, the number of protons for an atom with 20 neutrons and 20 electrons will be 20.
The symbol for this atom is Ca which is Calcium.
Learn more about Atom here: brainly.com/question/6258301
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