One of the major differences between our common Physics models of energy change and realistic models of them is: a
In the Physics models, the acceleration due to gravity is rounded to a non-exact but easier to use number
b
In the Physics models, the velocities are only calculated at set intervals of time, instead of continuously
c
In the Physics models, the objects are assumed to have simplified shapes in order to make motion by acceleration easier to calculate
d
In the Physics models, we do not take into account the energy change by the friction of moving components

Up of elements with the same number of valence electrons. vertical column in the periodic table of elements such as alkali metals or halogens. a horizontal row of elements in the periodic table. this is a characteristic of the elements in the periodic table that shows a pattern. it may increase or decrease across or down the table. periodic trend these are the highly reactive elements located in group 1 of the periodic table. these elements have one electron in their outer energy level which makes them highly reactive with water and halogens. these are the reactive elements located in group 2 of the periodic table. these elements have two electrons in their outer energy level which makes them reactive with water and halogens. alkaline earth metals these are the group 3 or d-block elements. these dense metals with high boiling points can have different oxidation states and all are solid at room temperature with the exception of mercury. transition metals this is the highly reactive family of elements with 7 valence electrons. this is an element with full valence shell, very unreactive. this is a group of elements with few valence electrons that conducts heat and electricity. one of a class of elements having properties intermediate to metals and nonmetals. this is a type of element that has many valence electrons, not a conductor.