Farly scientists performed experiments regarding mass and products for many years, but had difficulty demonstrating that mass was
conserved. This changed when they conducted these experiments
under specific conditions. What condition was this? Refer to
Paragraph 4.
А
They conducted experiments with specific gases.
B
They conducted experiments with specific types of wood.
с
They created scales that gave more precise measurements.
D
The experiments were conducted in sealed containers

i just got this problem. it's 90.3

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).

i'm pretty sure its b i might be wrong though!