Блок (таблица Менделеева)

Длинная таблица Менделеева, показывающая слева направо: s-, d-, f- и p-блоки. F-блок, обычно показываемый как сноска, здесь помещается между s- и d-блоками. ^[1]

Блок из периодической таблицы представляет собой набор элементов , объединенных орбиталей их валентные электроны или вакансии лежат в. ^[1] Термин , кажется, был впервые использован Чарльз Джанет . ^[2] Каждый блок назван в соответствии с его характеристической орбиталью: s-блок, p-блок, d-блок и f-блок.

Имена блоков (s, p, d и f) являются производными от спектроскопических обозначений для значения азимутального квантового числа электрона : резкое (0), главное (1), диффузное (2) или основное (3). Последующие обозначения идут в алфавитном порядке, как g, h и т. Д.

Характеристики [ править ]

Существует приблизительное соответствие между этой номенклатурой блоков, основанной на электронной конфигурации , и наборами элементов, основанными на химических свойствах. S-блок и p-блок вместе обычно считаются элементами основной группы , d-блок соответствует переходным металлам , а f-блок охватывает почти все лантаноиды (например, лантан ) и актиниды (например, актиний ). Не все согласны с точным составом каждого набора элементов. Например, элементы группы 12 цинк , кадмий и ртутьчасто рассматриваются как основная группа, а не переходная группа, потому что они химически и физически более похожи на элементы p-блока, чем другие элементы d-блока. В группе 3 элементов иногда рассматриваются основные элементы группы из - за их сходство с S-блочными элементами. Группы (столбцы) в f-блоке (между группами 2 и 3) не нумеруются.

Гелий представляет собой элемент s-блока с его внешними (и единственными) электронами на атомной орбитали 1s , хотя его химические свойства больше похожи на благородные газы p-блока в группе 18 из-за его полной оболочки.

v т е Блоки в периодической таблице
Группа  →	1	2		3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
↓  Период
1	1 ЧАС																		2 Он
2	3 Ли	4 Быть												5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg												13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca		21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr		39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba		71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra		103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
				57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb
				89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No
s-block p-block d-block f-block Background color shows the block of the periodic table Primordial  From decay  Synthetic Border shows natural occurrence of the element

s-block[edit]

The s-block is on the left side of the conventional periodic table and is composed of elements from the first two columns plus one element in the rightmost column, the nonmetals hydrogen and helium and the alkali metals (in group 1) and alkaline earth metals (group 2). Their general valence configuration is ns^1–2. Helium is an s-element, but nearly always finds its place to the far right in group 18, above the p-element neon. Each row of the table has two s-elements.

The metals of the s-block (from the second period onwards) are mostly soft and have generally low melting and boiling points. Most impart colour to a flame.

Chemically, all s-elements except helium are highly reactive. Metals of the s-block are highly electropositive and often form essentially ionic compounds with nonmetals, especially with the highly electronegative halogen nonmetals.

p-block[edit]

The p-block is on the right side of the standard periodic table and encompasses elements in groups 13 to 18. Their general electronic configuration is ns² np^1–6. Helium, though being the first element in group 18, is not included in the p-block. Each row of the table has a place for six p-elements except for the first row (which has none).

This block is the only one having all three types of elements: metals, nonmetals, and metalloids. The p-block elements can be described on a group-by-group basis as: group 13, the icosagens; 14, the crystallogens; 15, the pnictogens; 16, the chalcogens; 17, the halogens; and 18, the helium group, composed of the noble gases (excluding helium) and oganesson. Alternatively, the p-block can be described as containing post-transition metals; metalloids; reactive nonmetals including the halogens; and noble gases (excluding helium).

The p-block elements are unified by the fact that their valence (outermost) electrons are in the p orbital. The p orbital consists of six lobed shapes coming from a central point at evenly spaced angles. The p orbital can hold a maximum of six electrons, hence there are six columns in the p-block. Elements in column 13, the first column of the p-block, have one p-orbital electron. Elements in column 14, the second column of the p-block, have two p-orbital electrons. The trend continues this way until column 18, which has six p-orbital electrons.

The block is a stronghold of the octet rule in its first row, but elements in subsequent rows often display hypervalence. The p-block elements show variable oxidation states usually differing by multiples of two. The reactivity of elements in a group generally decreases downwards. This is not case in group 18, where reactivity increases in the following sequence: Ne < He < Ar < Kr < Xe < Rn < Og (although helium, which breaks the trend, is not a part of the p-block; therefore the p-block portion of group 18 conforms to the trend).

Oxygen and the halogens tend to form more ionic compounds with metals; the remaining reactive nonmetals tend to form more covalent compounds, although ionicity is possible when the electronegativity difference is high enough (e.g. Li3N). The metalloids tend to form either covalent compounds or alloys with metals.

d-block[edit]

The d-block is in the middle of the periodic table and encompasses elements from groups 3 to 12; it starts in the 4th period. Most or all of these elements are also known as transition metals because they occupy a transitional zone in properties, between the strongly electropositive metals of groups 1 and 2, and the weakly electropositive metals of groups 13 to 16. Group 3 or group 12, while still counted as d-block metals, are sometimes not counted as transition metals because they do not show the chemical properties characteristic of transition metals, for example, multiple oxidation states and coloured compounds.

The d-block elements are all metals and most have one or more chemically active d-orbital electrons. Because there is a relatively small difference in the energy of the different d-orbital electrons, the number of electrons participating in chemical bonding can vary. The d-block elements have a tendency to exhibit two or more oxidation states, differing by multiples of one. The most common oxidation states are +2 and +3. Chromium, iron, molybdenum, ruthenium, tungsten, and osmium can have oxidation numbers as low as −4; iridium holds the singular distinction of being capable of achieving an oxidation state of +9.

The d-orbitals (four shaped as four-leaf clovers, and the fifth as a dumbbell with a ring around it) can contain up to five pairs of electrons.

f-block[edit]

The f-block appears as a footnote in a standard 18-column table but is located at the center-left of a 32-column full width table. While these elements are generally not considered part of any group, some authors consider them to be part of group 3. They are sometimes called inner transition metals because they provide a transition between the s-block and d-block in the 6th and 7th row (period), in the same way that the d-block transition metals provide a transitional bridge between the s-block and p-block in the 4th and 5th rows.

The f-block elements come in two series, in periods 6 and 7. All are metals. The f-orbital electrons are less active in the chemistry of the period 6 f-block elements, although they do make some contribution:^[4] these are rather similar to each other. They are more active in the early period 7 f-block elements, where the energies of the 5f, 7s, and 6d shells are quite similar; consequently these elements tend to show as much chemical variability as their transition metals analogues. The later f-block elements behave more like their period 6 counterparts.

The f-block elements are unified by mostly having one or more electrons in an inner f-orbital. Of the f-orbitals, six have six lobes each, and the seventh looks like a dumbbell with a donut with two rings. They can contain up to seven pairs of electrons hence the block occupies fourteen columns in the periodic table. They are not assigned group numbers, since vertical periodic trends cannot be discerned in a "group" of two elements.

The two 14-member rows of the f-block elements are sometimes confused with the lanthanides and the actinides, which are names for sets of elements based on chemical properties more so than electron configurations. The lanthanides are the 15 elements running from lanthanum (La) to lutetium (Lu); the actinides are the 15 elements running from actinium (Ac) to lawrencium (Lr).

g-block[edit]

A g-block is predicted to begin in the vicinity of element 121. Though g-orbitals are not expected to start filling in the ground state until around element 124–126 (see extended periodic table), they are likely already low enough in energy to start participating chemically in element 121,^[5] similar to the situation of the 4f and 5f orbitals.

Symmetry[edit]

The four blocks can be rearranged such that they fit, equidistantly spaced, inside a regular tetrahedron.^[6]

See also[edit]

• Electron shell subshells

References[edit]

External links[edit]

The tetrahedral periodic table of elements. Animation showing a transition from the conventional table into a tetrahedron.