Chapter 3 – Atoms and the Periodic Table. 3.1 Atomic Structure. Atoms. Derived from the Greek word meaning “unable to divide”. They are the building blocks of molecules. Every element is made of tiny, unique particles that cannot be subdivided. Atoms of the same element are exactly the same.
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Atoms Derived from the Greek word meaning “unable to divide”. They are the building blocks of molecules.
Every element is made of tiny, unique particles that cannot be subdivided.
Atoms of the same element are exactly the same. Atoms of different elements can join to form molecules.
Nucleus The center of an atom; made up of protons and neutrons.
Proton A positively charged subatomic particle in the nucleus of the atom
Neutron A neutral subatomic particle in the nucleus of an atom.
Electron A tiny negatively charged subatomic particle moving around outside of an atom.
Atoms have no overall charge. Even though atoms have charged protons and electrons. They have an equal number of each. So, they cancel each other out.
Bohr’s Model In 1913, Neils Bohr suggested that electrons moves about a set path about the nucleus. The path defines the electron’s energy level.
Energy Level Any of the possible energies of an electron may have in an atom.
Modern theory states that electrons behave more like waves. In 1925, Bohr proposed a new model, that the electrons do not follow a set path.
Although we cannot know how the electron travels around the nucleus we can know where it spends the majority of its time (thus, we can know position but not trajectory).The “probability” of finding an electron around a nucleus can be calculated.Relative probability is indicated by a series of dots, indicating the “electron cloud”.
Orbital A region in an atom where there is a high probability of finding electrons.
s - orbital - Simplest orbital. - Can only have one orientation in space, because its shaped like a sphere.
Its shape enables it to surround the nucleus. • 90% electron probability/cloud for 1s orbital (notice higher probability toward the center) • It can hold a maximum of 2 electrons.
p - orbital • it is a dumbbell-shaped and can be oriented in 3 different ways in space. (3-Dimensions)
d - orbital • a more complex orbital. • There are a possible of 5 orientations.
All orbitals are very different in shape, each can contain a maximum 2 electrons. • Can contains a total of 10 electrons in all.
Four of the d orbital’s resemble two dumbbells in a clover shape. The last d orbital resembles a p orbital with a donut wrapped around the middle.
f - orbital • a more complex orbital. • There are a possible of 7 orbitals.
All orbitals are very different in shape, each can contain a maximum 2 electrons. • Can contains a total of 14 electrons in all.
And within each energy level, electrons occupy orbitals with the lowest energy.
An s orbital has the lowest energy. A p orbital has slightly more energy, followed by a d orbital. An forbital has the greatest energy.
Valence Electron An electron in the outermost energy level of an atom.
Periodic Law Properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number, or number of protons in their atoms.
Period A horizontal row elements in the periodic table.
As you move across a row the # of protons increases by 1. As does the # of electrons.
Group (family) – a vertical column of elements in the periodic table
These elements are not exactly alike, they have a different # of protons and electrons.
Some atoms form ions Some atoms may under go ionization.
Ionization The process of adding electrons to or removing electrons from an atom or groups of atoms. These are valence electrons.
Ions An atom or a group of atoms that has lost or gained 1 or more electrons and therefore has a net charge.
Cation An ion with a positive charge
Example: Lithium atom Lithium is so reactive, it reacts with air. It has 1 electron in the outer level of the s orbital. This one electron makes very reactive.
Removing this electron forms a positive ion (Li+) Li+ is less reactive, because now its outer energy level is full.
Anion An ion with a negative charge.
Example: Fluorine atom Fluorine is also very reactive; however it gains an electron to become less reactive.
It has 7 valence electrons and needs only 1 to complete its outer energy level. Therefore, easily gaining 1 electron & becoming a negative ion (F-).