The atomic number of an element is the number of protons the element has, so the element with the atomic number 55 has 55 protons.
Answer:

Explanation:
The speed increased from 2.0 * 10^7 m/s to 4.0 * 10^7 m/s over a 1.2 cm distance.
Let us find the acceleration:


Electric force is given as the product of charge and electric field strength:
F = qE
where q = electric charge
E = Electric field strength
Force is generally given as:
F = ma
where m = mass
a = acceleration
Equating both:
ma = qE
E = ma / q
For an electron:
m = 9.11 × 10^{-31} kg
q = 1.602 × 10^{-19} C
Therefore, the electric field strength of the electron is:


For displacement apply Pythagorean theorem



Answer:
PART A
In a solid
The attractive forces keep the particles together tightly enough so that the particles do not move past each other. ... In the solid the particles vibrate in place. Liquid – In a liquid, particles will flow or glide over one another, but stay toward the bottom of the container.
In a liquid
Particles are quite close together and move with random motion throughout the container. Particles move rapidly in all directions but collide with each other more frequently than in gases due to shorter distances between particles.
A gas
The particles move rapidly in all directions, frequently colliding with each other and the side of the container. With an increase in temperature, the particles gain kinetic energy and move faster.
PART B
The molecules are continually colliding with each other and with the walls of the container. When a molecule collides with the wall, they exert small force on the wall The pressure exerted by the gas is due to the sum of all these collision forces. The more particles that hit the walls, the higher the pressure.
Explanation:
GOOD LUCK!!! :)
It's difficult to measure that because it's hard to make sure it is only a uniform layer of gas in whatever you're measuring it in