Copper and Chromium have 1 electron in the 4s subshell, and 5 and 10 in the 3d subshell respectively. You needn't know beyond that until University.
Elements in a family, or group, of the periodic table share similar chemical properties due to their valence electron configurations. For example, alkali metals (Group 1) have one valence electron, making them highly reactive and eager to lose that electron to achieve a stable electron configuration. In contrast, noble gases (Group 18) have a full set of eight valence electrons, making them largely inert and unreactive. Despite their differing reactivity, both groups exhibit predictable behavior based on their electron arrangements.
Elements in the tall columns of the periodic table are called representative elements because they exhibit a wide range of physical and chemical properties that are representative of the overall characteristics of the elements in their respective groups. These elements include groups 1, 2, and 13-18, which display predictable behaviors in bonding and reactivity due to their valence electron configurations. Their diverse properties make them key examples for understanding the trends and patterns within the periodic table.
There are 7 known elements with full electron shells, six of which are referred to as noble gases because they are, generally, unreactive with other elements because of their full electron shells (their full electron shells make them resistant to forming bonds with other atoms to form molecules): Helium, Neon, Argon, Krypton, Xenon, and Radon. Ununoctium (element 118) also has a full electron shell, but due to relativistic effects is believed to be a solid at room temperatures (if there were enough atoms of it; it is extremely unstable with a half-life of less than a tenth of a second) so may not be considered a noble gas (all the other known elements with full electron shells are gases at room temperature) but, discounting radioactive decay which causes Ununoctium atoms to fission into lighter, reactive ones, is not chemically reactive with other elements.
Elements in group 17 of the periodic table, known as the halogens, are likely to form anions with a -1 charge. Examples include fluorine, chlorine, and iodine. These elements have 7 valence electrons and tend to gain one electron to achieve a stable electron configuration.
In the periodic table, elements are generally arranged by increasing atomic number, but some are out of order based on atomic mass due to isotopes and electron configurations. Notably, elements like potassium (K) and argon (Ar) are examples where potassium (atomic mass ~39.1) appears before argon (atomic mass ~39.9), even though argon has a higher atomic mass. This occurs because the periodic table prioritizes the atomic number (number of protons) over atomic mass when ordering elements. Other examples include isotopes and the placement of certain transition metals.
All of the representative elements (s and p block) have predictable electron configurations. However, many of the transition elements have electron configurations that are not predicted by the rules for determining electron configuration.
Transition metals have ground-state electron configurations that differ from the predicted ones due to the exchange of electrons between the ns and (n-1)d subshells. This exchange stabilizes the d orbitals, leading to configurations that are closer to half-filled or fully filled d subshells. Examples include chromium ([Ar] 3d^5 4s^1) and copper ([Ar] 3d^10 4s^1).
Examples of monovalent elements include hydrogen, sodium, and potassium. These elements have one valence electron, which allows them to easily form ions with a +1 charge.
Elements in a family, or group, of the periodic table share similar chemical properties due to their valence electron configurations. For example, alkali metals (Group 1) have one valence electron, making them highly reactive and eager to lose that electron to achieve a stable electron configuration. In contrast, noble gases (Group 18) have a full set of eight valence electrons, making them largely inert and unreactive. Despite their differing reactivity, both groups exhibit predictable behavior based on their electron arrangements.
Elements in the tall columns of the periodic table are called representative elements because they exhibit a wide range of physical and chemical properties that are representative of the overall characteristics of the elements in their respective groups. These elements include groups 1, 2, and 13-18, which display predictable behaviors in bonding and reactivity due to their valence electron configurations. Their diverse properties make them key examples for understanding the trends and patterns within the periodic table.
Noble gases. They are colorless, odorless, and have low chemical reactivity due to their stable electron configurations. They are commonly used in applications such as lighting, cooling, and insulation.
There are 7 known elements with full electron shells, six of which are referred to as noble gases because they are, generally, unreactive with other elements because of their full electron shells (their full electron shells make them resistant to forming bonds with other atoms to form molecules): Helium, Neon, Argon, Krypton, Xenon, and Radon. Ununoctium (element 118) also has a full electron shell, but due to relativistic effects is believed to be a solid at room temperatures (if there were enough atoms of it; it is extremely unstable with a half-life of less than a tenth of a second) so may not be considered a noble gas (all the other known elements with full electron shells are gases at room temperature) but, discounting radioactive decay which causes Ununoctium atoms to fission into lighter, reactive ones, is not chemically reactive with other elements.
Elements with similar electronegativities and valence electron configurations are likely to combine chemically. This is because they tend to form stable compounds by either sharing electrons (covalent bonding) or transferring electrons (ionic bonding) to achieve a more stable electron configuration. Examples include hydrogen and oxygen combining to form water (H2O) through covalent bonding, or sodium and chlorine combining to form sodium chloride (NaCl) through ionic bonding.
Elements in group 17 of the periodic table, known as the halogens, are likely to form anions with a -1 charge. Examples include fluorine, chlorine, and iodine. These elements have 7 valence electrons and tend to gain one electron to achieve a stable electron configuration.
In the periodic table, elements are generally arranged by increasing atomic number, but some are out of order based on atomic mass due to isotopes and electron configurations. Notably, elements like potassium (K) and argon (Ar) are examples where potassium (atomic mass ~39.1) appears before argon (atomic mass ~39.9), even though argon has a higher atomic mass. This occurs because the periodic table prioritizes the atomic number (number of protons) over atomic mass when ordering elements. Other examples include isotopes and the placement of certain transition metals.
Atoms that form ionic compounds typically involve elements with large differences in electronegativity. This results in one atom donating electrons to another to achieve stable electron configurations. Common examples include metals like sodium donating electrons to nonmetals like chlorine to form sodium chloride.
Elements in group 17 need one electron to gain a stable electron configuration. Two atoms of the same element or two elements in this family forms compounds with a single covalent bond. Examples are chlorine, bromine or iodine chloride.