Which of the following statements is true? group of answer choices elements in the same group have the same number of electron shells. elements in the same period have the same number of valence electrons. elements in the same group, or family, have similar characteristics, like reactivity and valence electrons. elements in the same period have similar characteristics, like reactivity and valence electrons.

Elements in the same group, or family, have similar characteristics, like reactivity and valence electrons.  

Explanation:

For example, elements in Group 1 all have one valence electron. They are reactive metals and form ions with a charge of +1.

A is wrong. As you go down a group, each successive atom adds one more valence shell of electrons.

B is wrong. The number of valence electrons changes as you go from left to right across a period.

D is wrong. As you go from left to right across a period, the elements gradually change from metals to metalloids and then to nonmetals.

trigonal pyramidal

tetrahedral

trigonal planar

bent

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.