![]() ![]() Trend Across the Period: As we move from left to right in a period, the electron affinity increases.Trend Across the Group: As we move from top to bottom in a group, electron affinity decreases.Reason: Nuclear charge increases but the number of shells remains the same.ĮLECTRON AFFINITY: The amount of energy required to add an electron to an atom is called electron affinity. Trend Across the Period: As we move from left to right in a period, the atomic radius decreases gradually.Reason: There are two reasons for the increase in atomic radius across the group that is increasing the number of shells and an increase in nuclear charge. Trend Across the Group: Atomic radius increases when we move from top to bottom in a group.ĪTOMIC RADIUS: The distance between the center of the nucleus of an atom and its valence shell is called the atomic radius. The main periodic trends followed by the elements in the periodic table of elements are based on some of the properties of chemical elements that are discussed below. These are metals with high melting points and have several oxidation states. Example: Transition Elements.į-Block elements are those elements that have their outermost electrons in f-orbitals. These elements produce colored salts and have high melting or boiling points. Example: Carbon, Oxygen, and Sulfur.ĭ-Block elements are those elements that have their outermost electrons in d-orbitals. ![]() These elements form covalent bonds by the mutual sharing of electrons. P-Block elements are those elements that have their outermost electrons in p-orbitals. Example: Alkali metals and Alkaline Earth Metals. These elements have low melting points, are more electropositive, chemically active, and are soft. ![]() S-Block elements are those elements that have their outermost electrons in s-orbitals. → They all are naturally occurring radioactive elements.Īll the chemical elements of the periodic table of elements are arranged in four specific blocks that described the position of the element’s outermost electron in a specific orbital. → They all are f-block elements and inner transition elements.įr, Ra, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr, Rd, Db, Sg, Bh, Hs, Mt, Ds, Rg, Cn, Uut, Fl, Uup, Lv, Uus, and Uuo. → They all have the same general structure and a radioactive element Tc is also included in this period.Ĭs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At, and Rn. Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sn, Te, I, and Xe. → They all belong to the first period whose valence shell electrons lie in characteristic d-block orbital thus named as D-block elements. K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, and Kr. Unfortunately, there was a slightly different system in place in Europe.→ They have electrons in both s and p orbitals. The first two groups are 1A and 2A, while the last six groups are 3A through 8A. The traditional system used in the United States involves the use of the letters A and B. There are two different numbering systems that are commonly used to designate groups, and you should be familiar with both. These two rows are pulled out in order to make the table itself fit more easily onto a single page.Ī group is a vertical column of the periodic table, based on the organization of the outer shell electrons. Periods 6 and 7 have 32 elements, because the two bottom rows that are separate from the rest of the table belong to those periods. Period 1 has only two elements (hydrogen and helium), while periods 2 and 3 have 8 elements. ![]() A new period begins when a new principal energy level begins filling with electrons. There are seven periods in the periodic table, with each one beginning at the far left. \) (Credit: User:Cepheus/Wikimedia Commons Source: (opens in new window) License: Public Domain)Ī period is a horizontal row of the periodic table. ![]()
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