How do the nuclei of covalently bonded atoms keep the bond together?
a. neutral particles in the nucleus provide enough mass that the force of gravity holds the atoms together
b. neutral particles in the nucleus can become positive or negative in order to balance the charges
c. positive particles in the nucleus change into negative particles that enter electron shells
d. positive particles in the nucleus are attracted to shared electrons, so the atoms stay close together

Answer;

D. Positive particles in the nucleus are attracted to shared electrons, so the atoms stay close together

Explanation;

-Covalent bonds hold atoms together because the attraction between the positively charged nuclei and the negatively charged shared electrons is greater than the repulsions between the nuclei themselves.

-The attraction between the positively charged nuclei and the negatively charged shared electrons is greater than the repulsions between the nuclei themselves.

-As two atoms approach each other, the electrons in their outer shells start to notice the nucleus of the other atom. As a result, they become attracted not only to their own nucleus, but to the nucleus of the other atom as well. The electrons then tend to spend more of their time in between the two nuclei, instead of just around their own nucleus.

D. Positive particles in the nucleus are attracted to shared electrons, so the atoms stay close together

Explanation:

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s