元素周期表的周期和组的特征
现代元素周期表中元素的物理和化学性质在整个周期和组中表现出一致的变化。元素的几个属性,例如价电子数、化合价、原子大小和金属字符,随着你在一个周期内从左到右移动而变化。当您从小组的顶部移动到底部时,这些品质会发生变化。元素周期表元素的这些特性将在下面更详细地讨论。
什么是现代元素周期表?
据说现在的元素周期表是玻尔发明的。它也被称为较大形式的元素周期表。元素按原子序数升序排列在现代表格中称为周期的水平行中。具有相同价电子数的其他元素在每个元素下方分组,以便具有相同价电子数的所有元素在同一垂直列中,称为一个组。
The modern periodic table arranges the elements according to their atomic numbers. “The properties of elements are a periodic function of their atomic numbers,” according to the modern periodic law. This means that elements with the same properties will occur at regular intervals or periods if atoms are organised in tabular form by increasing atomic numbers.
当原子通过增加原子序数来组织时,元素的电子配置显示出规则的周期性。元素电构型的周期性导致元素化学性质的周期性。具有相似化学性质的元素之间的电子配置相似。
- 周期——周期是元素周期表中元素的水平行。元素周期表中有七个周期。元素周期表中元素的原子序数是连续的。每次的元素数量都不一样。一个周期内的元素数量由原子的各种壳层中可容纳的最大电子数决定。
- 组- 组是元素周期表中的垂直列。在元素周期表的长形式中,有 18 个组。组中的元素没有相同的原子序数。第 1 组在元素周期表的左侧,而第 18 组在右侧。
元素周期表中周期的特征
在元素周期表的一个周期中从左到右移动,即在元素周期表的水平行中从左到右移动,我们将讨论元素的一些重要性质的变化,包括价电子数,化合价、原子大小和金属字符。这些变化将在下面进一步解释。
价电子
The number of valence electrons in elements increases from 1 to 8 as a period progresses from left to right, while it increases from 1 to 2 in the first period.
元素钠(Na)在第三周期包含一个价电子,而元素氩(Ar)具有八个价电子。每个周期的第一个元素都有一个价电子,每个周期的最后一个元素有八个价电子,但第一个周期除外,最后一个元素氦 (He) 只有两个价电子。
随着元素的电子构型随时间变化,原子最外层的电子数量从 1 个增加到 8 个。沿着周期,价电子数从1个增加到8个。一个周期内元素的原子序数也是连续的。例如,从钠到氩的第三周期元素的原子序数从 11 到 18 不等。Elements of the third period Na Mg Al Si P S Cl Ar Electronic configurations 2, 8, 1 2, 8, 2 2, 8, 3 2, 8, 4 2, 8, 5 2, 8, 6 2, 8, 7 2, 8, 8 Number of valence electrons 1 2 3 4 5 6 7 8
价
The valency of elements increases from 1 to 4 and eventually decreases to zero as you move from left to right in a period.
钠的化合价为 1,镁的化合价为 2,铝的化合价为 3,硅的化合价为 4,磷的化合价为 3,硫的化合价为 2,氯的化合价为 1,以及氩在第三周期的化合价为 0。化合价从 1 增加到 4,然后在一段时间内从左到右减少到零。在元素周期表的第三个周期中,化合价从钠的 1 增加到硅的 4,然后在氩中降低到零。结果,来自同一时期的元素的化合价不同。元素的化合价取决于一个原子为获得最接近的惰性气体电子构型而失去、获得或共享的电子数。Elements of the third period Na Mg Al Si P S Cl Ar Electronic configurations 2, 8, 1 2, 8, 2 2, 8, 3 2, 8, 4 2, 8, 5 2, 8, 6 2, 8, 7 2, 8, 8 Valency 1 2 3 4 3 2 1 0
原子大小
In a period, the atomic size decreases from left to right. The number of protons and electrons increases over time as the atomic number increases, therefore the extra electrons are added to the same shell. The electrons are drawn in closer to the nucleus due to the strong positive charge on the nucleus, and the atom’s size shrinks. As a result, there is a stronger attraction to the nucleus. Hence, the atomic size shrinks.
因此,在任何时期,元素周期表最左边的碱金属原子(锂、钠、钾等)最大,而最右边的卤素原子(氟、氯、溴等)元素周期表中,不包括惰性气体,是最小的。然而,另一方面,惰性气体的原子比它前面的卤素原子大。
金属字符
当你从左向右移动时,元素的金属字符会降低,而非金属字符会增加。第三阶段的金属包括钠、镁和铝。硅具有介于金属和非金属之间的特性,使其成为准金属。磷、硫和氯是非金属元素。
The components on the extreme left side of a period have the most metallic character, whereas the elements on the extreme right side of a period have the most non-metallic character. Metals are known as electropositive elements because they lose electrons and generate positive ions.
Non-metals, on the other hand, receive electrons and create negative ions, giving them the name electronegative elements. The atomic size shrinks from left to right over time as the nuclear force of attraction increases. As a result, losing valence electrons is difficult. Hence, metals’ electropositivity decreases over time. A non-metal atom can also easily gain electrons.
结果,非金属的电负性随时间增加。因此,钠是第三周期中最带正电的元素,而氯是最带负电的元素。Elements of the third period Na Mg Al Si P S Cl Nature of elements Metals Metalloid Non-metals
元素周期表中基团的特征
在一组元素周期表中从上到下移动,即在元素周期表的垂直列中从上到下移动,我们将讨论元素的一些重要性质的变化,包括价电子数,化合价、原子大小和金属字符。这些差异将在下面进一步解释。
价电子
Each element in a periodic table group has the same number of valence electrons. Lithium, sodium, and potassium, for example, all contain one valence electron in their atoms and belong to group 1 of the periodic table. Lithium, sodium, and potassium atoms can easily lose their one valence electron to create potassium ions with one unit positive charge, Li, Na, and K, respectively.
结果,第 1 组元素是一价的,化合价为 1。在它们的原子中,第 2 组中的所有元素都有两个价电子。除氦原子中只有两个价电子外,13族元素有3个价电子,14族元素有4个价电子,15族元素有5个价电子,16族元素有6个价电子,17族元素有七个价电子,第 18 族元素有八个价电子。结果,当你向下移动元素周期表时,元素中的价电子数保持不变。
价
All elements in a group have the same valency because the number of valence electrons that determine valency is the same. Lithium, sodium, and potassium, for example, all have one valence electron, hence all the elements in group 1 have the same valency of one.
第 1 组元素的化合价为 1,第 2 组元素的化合价为 2,第 13 组元素的化合价为 3,第 14 组元素的化合价为 4,第 15 组元素的化合价为 3,第 16 组元素的化合价为化合价为 2,第 17 组元素的化合价为 1,第 18 组元素的化合价为 0。因此,每个组的化合价相同。
原子大小
The size of atoms or atomic size grows as one moves down a group of the periodic table. When we proceed down in group 1 from top to bottom, the size of the atoms gradually increases from lithium to francium. Every time we proceed from the top to the bottom of a group, a new shell of electrons is added to the atoms.
结果,原子中电子壳层的数量稳步增加,导致原子尺寸也增加。因此,最小的原子大小可以在组的顶部找到,而最大的原子大小可以在底部找到。例如,在第 1 组中,锂 (Li) 是最小的元素,而钫 (Fr) 是最大的元素。 Atomic size increases on going down the groupLi Smallest atom Na K Rb Cs Fr Biggest atom
金属字符
The metallic character of elements increases as you move from top to bottom, while the non-metallic character decreases. The elements in the bottom half of the group have the most metallic character. For instance, the metallic nature of group 1 increases from lithium to francium. Every time we move down a group of the periodic table, one more electron shell is added, and the size of the atoms grows.
价电子远离原子核,原子核对价电子的控制减弱。结果,原子可以更快地失去价电子并产生正离子,从而增加其电正性。此外,随着原子的大小随着它们在组中的前进而变大,原子核变得更加嵌入原子中。原子核对传入电子的吸引力降低,使原子难以产生负离子并降低负电特性。
示例问题
问题一:第三期中哪个元素的尺寸最大?
回答:
In a period, the atomic size decreases from left to right. This indicates that the element to the left of the period is the largest, while the element to the right of the period is the smallest. The element on the left in the third period is sodium, hence sodium (Na) has the largest size in the third period.
问题 2:在一段时间内失去电子的趋势是什么?
回答:
The nuclear charge grows as the number of protons increases over a period, and the valence electrons are drawn in more strongly by the nucleus, making it more difficult for the atoms to lose electrons. As a result, as a period progresses from left to right, the tendency of atoms to lose electrons decreases.
问题3:第2族元素的通常价电子和化合价是多少?
回答:
The elements of group 2 are beryllium, magnesium, calcium, strontium, barium, radium. All these elements have electrons in their outermost shell, so the valence electrons of the elements of group 2 are 2. Since there are two valence electrons,m so these elements can easily lose 2 electrons, hence the valency of the elements of group 2 is 2.
问题4:元素属于元素周期表第2族,这个元素是金属还是非金属?
回答:
The metallic character of elements decreases as you move from left to right in a period. The components on the extreme left side of a period have the most metallic character. Since the elements of group 2 are on the left side of the table, so the given element is a metal.
问题 5:元素 A 的原子序数为 4,元素 B 的原子序数为 8,元素 C 的原子序数为 12。这些元素中哪一个成员同一族?
回答:
The number of valence electrons of elements in the group are the same. Elements Atomic Number Electronic configuration A 4 2, 2 B 8 2, 6 C 12 2, 8, 2
Clearly, elements A and C have 2 valence electrons. Hence they belong to the same group.