Block (periodic table) facts for kids
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Imagine the periodic table as a big map of all the elements. Just like a map has different regions, the periodic table has "blocks." A block is a group of elements that are similar because of where their outermost electrons are located. These special electrons are called valence electrons.
The idea of blocks was first used by a scientist named Charles Janet. Each block is named after a specific type of electron orbital: s, p, d, f, and even a predicted g-block. These names (s, p, d, f) come from old words used to describe light from elements: sharp, principal, diffuse, and fundamental.
Contents
What are Periodic Table Blocks?
The way elements are grouped into blocks is based on their electronic configuration. This means it's about how their electrons are arranged. This arrangement also helps us understand their chemical properties.
- The s-block and p-block elements are often called main-group elements.
- The d-block elements are known as transition metals.
- The f-block elements are called inner transition metals. This group includes most of the lanthanides (like lanthanum and dysprosium) and the actinides (like uranium and einsteinium).
Sometimes, elements in group 12 (like zinc and mercury) are seen as main-group elements. This is because they act more like p-block elements than other d-block elements. Also, group 3 elements can sometimes be considered main-group elements because they are similar to s-block elements. However, they are still part of the d-block.
You might notice that the f-block elements don't have group numbers (columns). This is because they are placed between group 2 and group 3 on the periodic table.
Helium is an s-block element because its electrons are in the 1s orbital. But it acts like the noble gases in group 18 (p-block) because its outer electron shell is full.
The s-block
The s-block is on the left side of the periodic table. The "s" stands for "sharp." It includes hydrogen and helium, plus the alkali metals (in group 1) and alkaline earth metals (in group 2).
These elements usually have 1 or 2 electrons in their outermost 's' orbital. Each row (or period) of the periodic table has two s-block elements.
Most s-block metals (from the second period onwards) are soft. They also have low melting and boiling points. Many of them can make a flame change color.
Except for helium, all s-block elements are very reactive. The metals in this block are very good at losing electrons. They often form ionic compounds with nonmetals, especially with elements like halogens that easily gain electrons.
The p-block
The p-block is on the right side of the standard periodic table. The "p" stands for "principal." It includes elements from group 13 to group 18. These elements have electrons in their 'p' orbitals.
Helium is in group 18, but it's not part of the p-block. Each row of the table has space for six p-block elements, except for the first row, which has none.
This block is special because it contains all three types of elements:
- Metals (like aluminium)
- Nonmetals (like phosphorus)
- Metalloids (like silicon)
The p-block elements are grouped by their properties:
- Group 13: icosagens
- Group 14: crystallogens
- Group 15: pnictogens
- Group 16: chalcogens
- Group 17: halogens
- Group 18: noble gases (not including helium)
The 'p' orbital can hold up to six electrons. This is why there are six columns in the p-block. Elements in the first column of the p-block (group 13) have one p-orbital electron. Elements in the second column (group 14) have two, and so on, up to group 18, which has six p-orbital electrons.
Elements in the p-block often show different oxidation states. This means they can combine with other elements in various ways. The reactivity of elements in a group usually decreases as you go down the column.
The d-block
The d-block is in the middle of the periodic table. The "d" stands for "diffuse." It includes elements from group 3 to group 12. This block starts in the 4th period.
From the fourth period onwards, each row has space for ten d-block elements. Most of these elements are also called transition metals. They are like a bridge between the very reactive metals of groups 1 and 2 and the less reactive metals of groups 13 to 16.
All d-block elements are metals. Most of them have one or more electrons in their 'd' orbitals that can take part in chemical reactions. Because the energy levels of these d-orbital electrons are very close, the number of electrons involved in bonding can change.
This is why d-block elements often have two or more oxidation states. For example, iron can be +2 or +3. Some elements, like chromium and tungsten, can have very low oxidation states. Others, like iridium, can even reach very high ones, like +9, but only under special conditions.
The 'd' orbitals have complex shapes. Four of them look like four-leaf clovers. The fifth one looks like a dumbbell with a ring around it. These orbitals can hold up to ten electrons, which is why there are ten columns in the d-block.
The f-block
The f-block is usually shown as a separate section at the bottom of the periodic table. The "f" stands for "fundamental." In a full-width periodic table, it's located between group 2 and group 3. From the sixth period onwards, each row has space for fourteen f-block elements.
These elements are often called inner transition metals. They act as a transition between the s-block and d-block in the 6th and 7th rows. This is similar to how the d-block elements connect the s-block and p-block in earlier rows.
The f-block has two main series:
- The first series includes elements from lanthanum to ytterbium in period 6.
- The second series includes elements from actinium to nobelium in period 7.
All f-block elements are metals. In the period 6 f-block elements, the 'f' orbital electrons are less involved in chemical reactions. This makes these elements quite similar to each other. However, in the early period 7 f-block elements, the 'f' electrons are more active. This means these elements can show more chemical variety, similar to transition metals.
The f-block elements are special because they usually have one or more electrons in an inner 'f' orbital. The 'f' orbitals have very complex shapes and can hold up to fourteen electrons. This is why the f-block has fourteen columns. These elements are not given group numbers because their properties don't follow the usual up-and-down trends of groups.
The two 14-element rows of the f-block are sometimes confused with the lanthanides and the actinides. These are names for groups of elements based on their chemical properties, not just their electron configurations. The lanthanides and actinides actually have 15 elements each, including the first d-block element in their period (lutetium and lawrencium).
Scientists used to think that the f-block ended differently. But now, based on lots of evidence, it's clear that the f-block includes elements from La–Yb and Ac–No. This is supported by the International Union of Pure and Applied Chemistry (IUPAC).
The g-block
Scientists predict that a g-block will start around element 121. The "g" stands for the next azimuthal quantum number, 4. Even though g-orbitals might not start filling with electrons until around element 124–126, they are expected to be low enough in energy to be chemically active starting from element 121.
If the pattern of previous rows continued, the g-block would have eighteen elements. However, calculations suggest that the eighth period might not follow the same clear patterns as earlier periods. This means the blocks might be harder to define.
See also
