Which of the following statements about elements and atoms is true? A. Atoms are the smallest unit of an element.
B. Atoms are made of particles called elements.
C. Elements are made of more than one type of atom.
D. Elements are changed into atoms by a chemical reaction.

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A. Atoms are the smallest unit of an element.

Explanation:

The correct statement from the given choices is that atoms are the smallest unit of an element.

Atoms are the smallest particles that takes part in chemical reactions and they are made up of protons, neutrons and electrons.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j