Dmitri Mendeleev developed a chart-like arrangement of the elements called the . He stated that if the elements were listed in order of increasing , their properties repeated in a regular manner. He called this the of the elements. The arrangement used today differs from that of Mendeleev in that the elements are arranged in order of increasing . Each horizontal row of elements is called a(n) . Each vertical column is called a(n) , or , because of the resemblance between elements in the same column, a(n) .

Explanation:

Dmitri Mendeleev developed a chart-like arrangement of the elements called the Periodic Table . He stated that if the elements were listed in order of increasing atomic mass, their properties repeated in a regular manner. He called this the periodicity of properties of the elements. The arrangement used today differs from that of Mendeleev in that the elements are arranged in order of increasing atomic number. Each horizontal row of elements is called a(n)period . Each vertical column is called a(n) column, or , because of the resemblance between elements in the same column, a(n) __group.

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.