A substance that cannot be broken down any further by chemical reactions. -All matter is made up of elements -There are 92 naturally occiring elements. -Elements are made of atoms. -Each element has a symbol, made of letters from its name.
Smallest particle of an element that still retains chemical and physical properties of the element. -Atoms of the same element share similar chemical properties -Atoms are made up of sunbatomic particles.
Tiny particles that make up an atom. The three most stable are protons, neutrons,and electrons.
A subatomic particle. It makes up part of the nucleus, and has no charge. It is calculated when measuring atomic mass, and has about the same weight as a proton.
A subatomic particle. it makes up part of the nucleus, and has a positive charge. It is calculated when measuring atomic mass, and has about the same weight as a proton.
A subatomic particle. It orbits around the nucleus, held in place by the electrostatic attractions of the positive protons. It is not calculated when measuring atomic mass, because its own mass is so tiny.
Number of protons in an atom of a particular element. Every atom has an equal number of protons and electrons, therefore having no overall charge. All atoms of an element have the same atomic number.
The number of protons and neutrons in an atom = the approximate mass of the whole atom. The mass of a proton = the mass of a neutron. Atomic mass measured in amu. Mass number - Atomic number = number of neutrons. Number of neutrons can vary in an element, but number of protons is constant.
Atoms of an element that have the same atomic number but a different mass number. Same number of protons, different number of neutrons. Naturally, elements occur as mixed isotopes. Different isotopes of the same element react chemically in the same way. Some isotopes are radioactive. The nucleus decays, giving off particles and energy. The atom is transformed into a different atom.
Energy levels of Electrons
Electorns are the only stable subatomic particles to be involved in chemical reactions. The further away from the nucleus, the greater their potential energy. Levels of potential energy are called electron shells. An orbital is the 3D space ewhere and electron si found 90% of the time.
First Energy Level of Electrons
Has one spherical s orbital. Holds a maximum of two electrons.
Second Energy Level of Electrons
Holds a maximum of eight electrons. Has one more s orbitals. (2s orbital) Three dumbbell-shaped orbitals each oriented at right angles to the other two (2px, 2py, 2pz orbitals).
Higher Energy Levels of Electrons
Contain s and p orbitals Contain additional orbitals with more complex shapes
Reactons of Atoms with Different Valence Shells
An atom with a complete valence shell is unreactive or inert An atom with an incomplete valence shell is chemically reactive (tends to form chemical bonds until it has eight electrons to fill the valence shell). Atoms with the same number of valence electrons show similar chemical behavior.
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