periodic table ' periodic table valence electrons

Calcium is essential to the human body it is absorbed and used for a number of processes, including strengthening bones. A familiar example of an element that you must take in is calcium (Ca). While your body can assemble many of the chemical compounds needed for life from their constituent elements, it cannot make elements. An element is a pure substance that is distinguished from all other matter by the fact that it cannot be created or broken down by ordinary chemical means. Elements and CompoundsĪll matter in the natural world is composed of one or more of the 92 fundamental substances called elements. A piece of cheese that weighs a pound on Earth weighs only a few ounces on the moon. In other words, weight is variable, and is influenced by gravity. An object of a certain mass weighs less on the moon, for example, than it does on Earth because the gravity of the moon is less than that of Earth. Where gravity strongly pulls on an object’s mass its weight is greater than it is where gravity is less strong. An object’s weight, on the other hand, is its mass as affected by the pull of gravity. An object’s mass is the amount of matter contained in the object, and the object’s mass is the same whether that object is on Earth or in the zero-gravity environment of outer space. An object’s mass and its weight are related concepts, but not quite the same. Scientists define matter as anything that occupies space and has mass. The substance of the universe-from a grain of sand to a star-is called matter. Explain how electrons occupy electron shells and their contribution to an atom’s relative stability.

Identify the key distinction between isotopes of the same element.Distinguish between atomic number and mass number.Discuss the relationships between matter, mass, elements, compounds, atoms, and subatomic particles.By the end of this section, you will be able to:

Periodic table ' periodic table valence electrons