What is the trend in effective nuclear charge for elements on the periodic table?
it decreases across a period but is constant down a group.
it increases across a period but is constant down a group.
it is constant across a period but decreases down a group.
it is constant across a period but increases down a group.

Which are causes of mechanical weathering? check all that apply.oacid raino plant growtho animal actionso carbon dioxideo pressure release

The characteristic of two different types of reactions are shown below. reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of and element. which statement is true about the atoms of the elements that participate in the two reactions? a: their identity changes in both reaction a and b. b: their identity changes in reaction a but not b. c: their identity changes in reaction b but not a. d: their identity remains the same.

Is a pencil falling to the floor anon contact force, a force, or a contact force