This pattern explains why the metals in the first group become +1, the ones in the second group become +2, and Al, for example, becomes +3. It is formed when an atom of Ca (1 s 22 s 22 p 6 3 s 23 p 6 4 s 2 or 4 s 2) loses two electrons from the outer shell 4s.Ĭa ( 4 s 2) ⟶ 2e − + Ca 2+() Let’s now determine the electron configuration of the Ca 2+ ion. The reason for this is that, remember, noble gases are very stable because of the low energy level of complete orbitals. In fact, this is the electron configuration of Ne, and we say that Na + and Ne are isoelectronic (same electronic structure). Notice that the ion has a configuration with a complete shell of p orbitals which is characteristic of noble gases. Therefore, the electron configuration of the Na + ion will be 1 s ☢ s ☢ p ⁶: The electron configuration of sodium is 1 s ☢ s ☢ p ⁶3 s ¹, and the electron is removed from the energy level with the greatest n value – 3 s. It is in the first group, so it loses one electron to become Na +. This electron is going to be from the outermost valence shell as these are the electrons farthest away from the nuclei and thus not as strongly attracted to it. Now, how do we determine the electron configuration of an ion? If it is, for example, a +1 charged cation, that means the atom has lost one electron. Notice that the number of protons is not changed, and the ions are charged because, unlike atoms, their number of protons and electrons is not equal.Įlectron Configuration of Main Group Cations Nonmetals tend to gain an electron(s) and become anions (negatively charged ions). Recall, this pattern for the formation of anions and cations: Metals tend to lose electron(s) and become cations (positively charged ions). For anions, the charge tells how many extra electrons there are compared to the number of protons. If it is a cation, then the positive indicates how many more protons it has compared to the number of electrons. The charge of the ion is a result of an imbalance between the number of protons and electrons. The first thing you need to remember here is that cations are formed by losing an electron(s), and anions are formed by gaining an electron(s). This is the very least you should know in addition to the order of filling the energy levels and sublevels so please go over the detailed post on the electron configurations before getting to ions. In this level, there are 2 electrons in an s orbital, and 5 electrons in the p orbital: Next, we have the orbitals in the second energy level because fluorine is in the second row of the periodic table. The 1 s 2 means there are 2 electrons in the s orbital that is in the first row. The letters ( s, p, d, f) tell us the type of the orbital, and the exponent is for the number of electrons. The number before each letter indicates the main energy level, and this is the principal quantum number, n. For example, the electron configuration of fluorine is1 s 22 s 22 p 5. However, it's easy to determine the configuration of electrons for heavier elements by making a chart.In the previous post, we talked about electron configurations, what they show, how to read, and how to write them based on energy levels and sublevels.Īs a reminder, electron configurations show the number and location of electrons in an atom or an ion. If there are more electrons than protons, the ion has a negative charge and is called an anion.Įlements are shown from atomic number 1 (hydrogen) up to 94 (plutonium). If there are more protons than electrons, an atomic ion has a positive charge and is called a cation. The isotope is defined by the number of neutrons in an atom, which might be equal to the number of protons-or not.Īn ion of an atom is one in which the number of protons and electrons is not the same. Remember, a neutral atom contains the same number of protons and electrons. The upper right side shows the number of electrons in a neutral atom. The element atomic number and name are listed in the upper left. The final ring or shell of electrons contains the typical number of valence electrons for an atom of that element. The electron shells are shown, moving outward from the nucleus. Here are electron shell atom diagrams for the elements, ordered by increasing atomic number.įor each electron shell atom diagram, the element symbol is listed in the nucleus. For that, we have electron shell diagrams. It's easier to understand electron configuration and valence if you can actually see the electrons surrounding atoms.
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