What Is The Periodic Table: Families and Periods

In the periodic table of elements, there are seven horizontal rows of elements called periods . The vertical columns of elements are called groups, or families . The most common way the periodic table is classified by metals, nonmetals, and metalloids.

Periods in the periodic table

In each period (horizontal row), the atomic numbers increase from left to right. The periods are numbered 1 through 7 on the left-hand side of the table.

Elements that are in the same period have chemical properties that are not all that similar. Consider the first two members of period 3: sodium (Na) and magnesium (Mg). In reactions, they both tend to lose electrons (after all, they are metals), but sodium loses one electron, while magnesium loses two. Chlorine (Cl), down near the end of the period, tends to gain an electron (it’s a nonmetal).

Families in the periodic table

Members of the families (vertical columns) in the periodic table have similar properties. The families are labeled at the top of the columns in one of two ways:

  • The older method uses Roman numerals and letters. Many chemists prefer and still use this method.
  • The newer method uses the numbers 1 through 18.

So why do the elements in the same family have similar properties? You can examine four families on the periodic table and look at the electron configurations for a few elements in each family.

The figure below lists some important families that are given special names:

  • The IA family is made up of the alkali metals . In reactions, these elements all tend to lose a single electron. This family contains some important elements, such as sodium (Na) and potassium (K). Both of these elements play an important role in the chemistry of the body and are commonly found in salts.
  • The IIA family is made up of the alkaline earth metals . All these elements tend to lose two electrons. Calcium (Ca) is an important member of the IIA family (you need calcium for healthy teeth and bones).
  • The VIIA family is made up of the halogens . They all tend to gain a single electron in reactions. Important members in the family include chlorine (Cl), used in making table salt and bleach, and iodine (I).
  • The VIIIA family is made up of the noble gases . These elements are very unreactive. For a long time, the noble gases were called the inert gases, because people thought that these elements wouldn’t react at all.A scientist named Neil Bartlett showed that at least some of the inert gases could be reacted, but they required very special conditions. After Bartlett’s discovery, the gases were then referred to as noble gases.


Valence electrons and families

An electron configuration shows the number of electrons in each orbital in a particular atom. These electron configurations show that there are some similarities among each group of elements in terms of their valence electrons.

Keep this in mind about the number of valence electrons and the Roman numeral column number: The IA family has 1 valence electron; the IIA family has 2 valence electrons; the VIIA family has 7 valence electrons; and the VIIIA family has 8 valence electrons. So for the families labeled with a Roman numeral and an A, the Roman numeral gives the number of valence electrons.

The Roman numeral makes it very easy to determine that oxygen (O) has six valence electrons (it’s in the VIA family), that silicon (Si) has four, and so on. You don’t even have to write the electronic configuration or the energy diagram to determine the number of valence electrons.

With the discovery of the periodic table, the study of individuals properties of the known elements is reduced to the study of a few groups. we will describe various attempts that were made to classify the elements into tabular form.
Doberreiner Triads
A German chemist Doberreiner observed the relationship between between atomic masses of severals groups of three elements called triads. In these groups, the central or middle element had atomic masses average of the other two elements.

What Is The Periodic Table: Families and Periods is an examination question from which students are usually afraid. The periodic table is an even cluster of the synthetic components sorted out by nuclear number, from the component with the least nuclear number, hydrogen to the component with the most noteworthy nuclear number. The nuclear number of a component is the number of protons in the core of a molecule of that component.

The vertical segments on the periodic table are called gatherings or families on account of their comparative substance conduct. All the individuals from a group of components have a similar number of valence electrons and comparable compound properties. The horizontal columns on the periodic table are called periods.

Analyzing the periodic table:

If you look at a periodic table, you will frequently locate a number composed over each gathering (section). These numbers fill in as names and gatherings are regularly alluded to by their names. Contingent upon the source or age of your periodic table, you may see two distinctive numbering frameworks for alluding to the families on the periodic table. In the more established framework, the numbers 1 – 18 and the letters An and B were utilized to name the gatherings. The more up to date show is to mark each gathering from 1 – 18 in the consecutive request. Notwithstanding, the more seasoned naming plan assists with giving more knowledge into the electron setups of each gathering. Accordingly, in this content we will utilize the more seasoned marking plan to introduce each gathering.


1) Alkali Metals or Group 1-A:

Gathering 1A (or IA) of the periodic table are the alkali metals: hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). These are (aside from hydrogen) delicate, glossy, low-liquefying, exceptionally responsive metals, which discolor when presented to air. The name originates from the way that when these metals or their oxides are disintegrated in water, a fundamental (basic) arrangement results. Since the antacid metals are responsive, they are only here and there (if at any time) found in their essential structure in nature and are generally found as ionic mixes (aside from hydrogen).

The alkali metals have just a single valence electron in their most elevated energy orbitals (ns1). In their particular periods, they are the biggest components and have the least ionization energies. The valence electron is handily lost, shaping a particle with a 1+ charge.

The salt metals are solids at room temperature (aside from hydrogen), yet have genuinely low softening focuses: lithium liquefies at 181ºC, sodium at 98ºC, potassium at 63ºC, rubidium at 39ºC, and cesium at 28ºC. They are likewise moderately delicate metals: sodium and potassium can be cut with a margarine blade.

Salts of the Group 1A components will in general be amazingly dissolvable in water. Since the antacid metal particles are moderately enormous (contrasted with different particles from a similar period), their charge densities are low and they are effortlessly isolated from their anions and solvated by polar solvents like water.

The alkali metals (once more, aside from hydrogen) respond enthusiastically with water, delivering the metal hydroxide, hydrogen gas and warmth.

2) Alkaline Earth Metals or Group 2-A:

Gathering 2A (or IIA) of the periodic table are the alkaline earth metals: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). They are more diligent and less responsive than the alkali metals of Group 1A. The name originates from the way that the oxides of these metals delivered fundamental arrangements when disintegrated in water and they remained solids at the temperatures accessible to the old chemists. Like the Group 1A components, the soluble earth metals are too receptive to ever be found in nature in their essential structure.

The basic earth metals have two valence electrons in their most noteworthy energy orbitals (ns2). They are more modest than the salt metals of a similar period and subsequently have higher ionization energies. By and large, the antacid earth metals are ionized to shape a 2+ charge.

The alkaline earth metals have a lot higher dissolving focuses than the salt metals: beryllium liquefies at 1287ºC, magnesium at 649ºC, calcium at 839ºC, strontium at 768ºC, barium at 727ºC and radium at 700ºC. They are more earnestly metals than the Group 1A components, yet are delicate and lightweight contrasted with a significant number of the change metals.

Salts of the Group 2A metals are less soluble in water than those of Group 1A as a result of the higher charge densities on the 2+ cations; all things considered, many Group 2A salts are in any event respectably dissolvable. Some Group 2A salts security firmly to water atoms and take shape as hydrates; among these are Epsom salt, MgSO4·7H2O, and gypsum, CaSO4·2H2O.

3) Halogens or Group 7-A elements:

They all will in general increase a solitary electron in responses. Significant individuals in the family incorporate chlorine (Cl), utilized in making table salt and dye, and iodine (I).

4) Noble Gases:

They are the most steady due to having the greatest number of valence electrons their external shell can hold.

Accordingly, they once in a while respond with different components since they are as of now steady.

Different attributes of the noble gases are that they all lead to power, fluoresce, are scentless, dry and are utilized in numerous conditions when a steady component is expected to keep up a sheltered and consistent climate.

This compound arrangement contains helium, neon, argon, krypton, xenon and radon.

The noble gases were recently alluded to as latent gases. However, this term isn’t carefully exact in light of the fact that few of them do participate in synthetic responses.


A period is a horizontal column of components on the periodic table. All components straight have a similar number of electron shells. Each next component in a period has one more proton and is less metallic than its archetype.