The Aufbau principle gives the order of electron filling in an atom. Electron configuration notation simplifies the indication of where electrons are located in a specific atom. 6.8: Quantum-Mechanical Orbitals and Electron Configurations We look at the four quantum numbers for a given electron.Orbitals are mathematically derived regions of space with different probabilities of having an electron. This field deals with probabilities since we cannot definitely locate a particle. 6.7: The Quantum-Mechanical Model- Atoms with Orbitals Quantum mechanics involves the study of material at the atomic level.That means that we rarely need to worry about the mass of a specific isotope, but instead we need to know the average mass of the atoms of an element. We use a mixture of the isotopes of an element in chemical reactions and other aspects of chemistry, because all of the isotopes of an element react in the same manner. 6.6: Atomic Mass- The Average Mass of an Element’s Atoms In chemistry we very rarely deal with only one isotope of an element.Atoms of the same element that differ in their numbers of neutrons are called isotopes. But some carbon atoms have seven or eight neutrons instead of the usual six. For example, all carbon atoms have six protons, and most have six neutrons as well. 6.5: Isotopes - When the Number of Neutrons Varies All atoms of the same element have the same number of protons, but some may have different numbers of neutrons.Most metals become cations when they make ionic compounds.

Positively charged ions are called cations. Atoms that lose electrons acquire a positive charge as a result because they are left with fewer negatively charged electrons to balance the positive charges of the protons in the nucleus.

6.4: Ions - Losing and Gaining Electrons Atom may lose valence electrons quite to obtain a lower shell that contains an octet.

Metals are also malleable (they can be beaten into thin sheets) and ductile (they can be drawn into thin wires). A metal is a substance that is shiny, typically (but not always) silvery in color, and an excellent conductor of electricity and heat. Every element can be classified as either a metal, a nonmetal, or a metalloid (or semi metal).

6.3: Looking for Patterns- The Periodic Table Certain elemental properties become apparent in a survey of the periodic table as a whole.This number is very important because it is unique for atoms of a given element. The number of protons in an atom is called its atomic number (Z). Since an atom of one element can be distinguished from an atom of another element by the number of protons in its nucleus, scientists are always interested in this number, and how this number differs between different elements. 6.2: Elements- Defined by Their Number of Protons Scientists distinguish between different elements by counting the number of protons in the nucleus.All atoms have the same number of electrons as protons, so the positive and negative charges 'cancel out', making atoms electrically neutral.

Electrons have an electric charge of −1, which is equal but opposite to the charge of a proton, which is +1. The mass of an electron is only about 1/2000 the mass of a proton or neutron, so electrons contribute virtually nothing to the total mass of an atom.

6.1: The Properties of Protons, Neutrons, and Electrons Electrons are extremely small.

Valence electrons periodic table trend