Unit 2 Lesson 4: Atomic Composition
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atom
the basic unit of a chemical element
electron
a negatively charged particle that is outside the nucleus of an atom
element
a pure substance that cannot be changed into simpler substances through chemical or physical means
ion
a charged particle that results when the number of protons and number of electrons differ
mass number
the sum of the protons and neutrons that make up the nucleus of an atom
neutron
a particle that has no charge that makes up the nucleus of an atom
proton
a positively charged particle that makes up the nucleus of an atom
stable
in atoms, the condition in which a nucleus is unlikely to undergo decay
Atoms are the fundamental building blocks of most of the matter you are familiar with. Atoms consist of three different types of particles:
• Protons are positively charged particles that lie in the center, or nucleus of the atom. • Neutrons are neutrally charged particles that lie in the atomic nucleus with the protons. • Electrons are negatively charged particles which lie on the outside of the atom.
What defines a particular element
What defines a particular element is the number of protons in its nucleus.
What defines a particular element is the number of protons in its nucleus. How many protons does hydroen and helim have
Hydrogen atoms have one proton, helium atoms have two protons, and so on.
Do all atoms contain the same number of neurtons in their nuclei
Different atoms of an element may contain different numbers of neutrons in their nuclei. For example, there are atoms of hydrogen that have one neutron and some that have two neutrons.
Protons and neutrons are similar in mass to each other but are much heavier than electrons. The mass number of a particular atom is the total number of protons and neutrons the atom contains. Example
So, a hydrogen atom with a single proton has a mass number of 1 and is named hydrogen-1. A hydrogen atom with 1 proton and 1 neutron has a mass number of 2 and is named hydrogen-2.
What factors must be in place to have a neutral atom
To have a neutral atom, the same number of protons and electrons must be present. The positive and negatively charged particles counteract each other to remain neutral.
Tell be about the neutrons in a neutral atom
A stable atom most likely also has the same number of neutrons. The number of neutrons do not affect the overall charge of the atom because neutrons have no charge.
Two atoms of the same element with different numbers of neutrons are called different
isotopes of that element
Give an example of differnt isotopes of hydrogen
For example, hydrogen-1 and hydrogen-2 are both hydrogen atoms, but hydrogen-1 contains no neutrons, while hydrogen-2 contains 1 neutron, so they are different isotopes.
Whether an atomic nucleus is stable or unstable depends on the
Whether an atomic nucleus is stable or unstable depends on the relative numbers of protons and neutrons in its nucleus.
The exact ratio that determines stability varies from
element to element.
Describe an unstable nucelus
An unstable nucleus is likely to undergo decay, meaning that it will give off particles and energy. This sometimes causes the atom to change into an atom of a different element.
The amount of positive charge carried by a single proton is equal in magnitude to the amount of
negative charge carried by a single electron.
. As stated above, an atom is neutrally charged if the number of protons equals the number of electrons. If the numbers are unequal, the atom will have a net charge and is called an
ion