Chapter 5 Glossary Terms
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What is an atom?
It is the smallest particle of an element that retains the identity of the element. In an atom contains protons, neutrons, and electrons. According to Dalton's Atomic Theory, all matter is made of atoms, which cannot be created, destroyed, or divided, every element has different atoms from each other, and compounds are created when atoms link together.
What is an electron?
A negatively charged particle in the atom. Electrons almost have no mass, and are found in all atoms.
What is a subatomic particle?
A particle that is smaller than the atom. e.g. electrons, neutrons, protons, neutrinos, etc. There are hundreds of subatomic particles!
What is the nucleus?
The positively charged, dense centre of an atom. It consists of protons and neutrons, and the electrons in the atom revolve around it.
What is a proton?
It is a positively charged subatomic particle that is part of every atomic nucleus, along with neutrons.
What is a neutron?
The uncharged subatomic particle that is part of almost every atomic nucleus, along with protons.
What is an atomic number?
The number of protons in the nucleus of an atom. The atomic number helps us find how many protons are in an element and what element it is. e.g. an atom has one proton, making its atomic number 1. The element with atomic number 1 is hydrogen.
What is a mass number?
The sum of the number of protons and the number of neutrons in the nucleus of an atom. The mass number is always a whole number. It is always written in the top left corner in the standard atomic notation.
What is an isotope?
One or two more forms of an element that have the same number of protons, but a different number of neutrons. For example, there is one hydrogen atom with one proton but no neutron (hydrogen-1), and another atom with one proton and one neutron (hydrogen-2). These are two different isotopes because they have different numbers of neutrons.
What is atomic mass?
The average mass of the naturally occurring isotopes of an element. The periodic table that Dimitri Mendeleev made was made according to increasing atomic mass.
What is the periodic table?
It is a system for organizing the elements into columns and rows, so that elements with similar properties are in the same column. The periodic table is useful for predicting properties of unknown elements based on properties of known elements.
What is a metal?
It is an element that is hard shiny, malleable, ductile, and it is s good conductor of heat & electricity. Elements on the left side of the periodic table are mostly metals (except hydrogen). e.g. aluminum, iron, magnesium...
What is a non-metal?
It is an element that is not shiny, malleable, or ductile, and is a poor conductor of heat & electricity. Non-metals are located on the right side of the periodic table. e.g. helium, oxygen, selenium...
What is a metalloid?
It is an element that shares some properties with metals and some properties with non-metals. Elements that make a diagonal line between the metals & non-metals on the periodic table are metalloids. e.g. boron, silicon, arsenic...
What is a period?
It is a horizontal row of elements in the periodic table. They are numbered from 1-7, from top to bottom.
What is a group?
It is a vertical column of elements in the periodic table. They are numbered from 1- 18, from the left side to the right side. A group is also called a family, because the elements in the group usually have similar chemical & physical properties.
What are valence electrons?
They are electrons in the outermost occupied energy level of an electron. Elements in the same group have the same number of valence electrons. The most reactive elements are groups 1 & 17, because they need one more/less valence electron to look like the nearest noble gas.
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