That means that it won't be as strongly attracted as in the fluorine case. (This is exactly the same sort of argument as you have seen in the atomic radius section above.) However, in the chlorine case, the nucleus is further away from that bonding pair. The bonding pair of electrons between the hydrogen and the halogen feels the same net pull of 7+ from both the fluorine and the chlorine. This is easily shown using simple dots-and-crosses diagrams for hydrogen fluoride and hydrogen chloride. The atoms become less good at attracting bonding pairs of electrons.Įxplaining the decrease in electronegativity Notice that electronegativity falls as you go down the Group. If you choose to follow this link, use the BACK button on your browser to return quickly to this page. Note: You will find electronegativity covered in detail in another part of this site. It is usually measured on the Pauling scale, on which the most electronegative element (fluorine) is given an electronegativity of 4.0. That means that the atoms are bound to get bigger as you go down the Group.Įlectronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Obviously, the more layers of electrons you have, the more space they will take up - electrons repel each other. The only factor which is going to affect the size of the atom is therefore the number of layers of inner electrons which have to be fitted in around the atom. The outer electrons always feel a net pull of 7+ from the centre. This is equally true for all the other atoms in Group 7. The positive charge on the nucleus is cut down by the negativeness of the inner electrons.

In each case, the outer electrons feel a net pull of 7+ from the nucleus. The pull the outer electrons feel from the nucleus. The number of layers of electrons around the nucleus You can see that the atomic radius increases as you go down the Group.

Note: You will find atomic radius covered in detail in another part of this site. The same ideas tend to recur throughout the atomic properties, and you may find that earlier explanations help to you understand later ones. H-Cl)Įven if you aren't currently interested in all these things, it would probably pay you to read the whole page. There is also a section on the bond enthalpies (strengths) of halogen-halogen bonds (for example, Cl-Cl) and of hydrogen-halogen bonds (e.g. You will find separate sections below covering the trends in atomic radius, electronegativity, electron affinity, melting and boiling points, and solubility. This page explores the trends in some atomic and physical properties of the Group 7 elements (the halogens) - fluorine, chlorine, bromine and iodine. Predict the melting and boiling points of astatine, and its state at room temperature.Atomic and physical properties of Periodic Table Group 7 (the halogens)ĪTOMIC AND PHYSICAL PROPERTIES OF THE GROUP 7 ELEMENTS (THE HALOGENS) Astatine is placed below iodine in group 7. The graph shows the melting and boiling points of the first four group 7 elements. more energy is needed to overcome these forces.the intermolecular forces become stronger.In group 7, the further down the group an element is, the higher its melting point and boiling point. The table shows the colour and physical states of chlorine, bromine and iodine at room temperature. In all groups of the periodic table, the further down the group an element is, the higher its relative molecular mass. Each molecule is made up of a pair of halogen atoms joined by a single covalent bond. The halogens show trends in their physical and chemical properties. Group 7 is on the right-hand side of the periodic table, next to group 0 The elements in group 7 are called the halogens. Group 7 contains non-metal elements placed in a vertical column on the right of the periodic table.

Group 7 reactivity trend