This contracts the radius inwards and therefore the atomic radius decreases. This means there is a stronger attraction between the nucleus and the electrons in the orbitals so the electrons are pulled inwards towards the nucleus. The nucleus gains a more positive charge as the number of protons increases. The proton number of the element increases as you move across a period which means that the number of protons increases. The atomic radius of an element decreases as you move across a period.In order to exemplify this, we will look at elements in Period 3: Periodicity – Trends along Period 3 Atomic Radius Trend Across Period 3 Periodicity refers to the repeating pattern in physical and chemical properties of the elements across a period of the periodic table. It does not store any personal data.Periodicity - Trends Along Period 3 (A-Level Chemistry) Periodicity The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category 'Performance'. This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category 'Other. The cookies is used to store the user consent for the cookies in the category 'Necessary'. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category 'Functional'. The cookie is used to store the user consent for the cookies in the category 'Analytics'. These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. The two atomic radius trends we discussed above are true for the majority of the periodic table of elements. The potassium atom has an extra electron shell compared to the sodium atom, which means its valence electrons are further from the nucleus, giving potassium a larger atomic radius. Why does potassium have a larger atomic radius than sodium? The six noble gases, in group 18 of the periodic table, are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). However, there are a few exceptions to these trends. An atomic radius is one-half the distance between the nuclei of two atoms.Īre there any exceptions to the atomic radius trend? A radius is the distance between the center of an object and its outer edge. Which is true about the radius of an atom?Īn atom is a basic unit of a chemical element, such as hydrogen, helium, potassium, etc. When an additional shell is added, those new electrons are farther from the atom’s nucleus, which increases atomic radius. The first atomic radius periodic trend is that atomic radii increase as you move downwards in a group. Why does atomic radius increase as you move down a group? The atomic radius of atoms generally increases from top to bottom within a group. The atomic radius of atoms generally decreases from left to right across a period. How do atomic radii vary in a group and period?

The growing size is due to the increasing number of filled electron shells as you move down the periodic table. The bigger the atomic number, the larger the atom’s radius. What affects the atomic radius?Īs the atomic number of an element increases, so does the size of its nucleus and the number of electrons around it. As we move from left to right across a period on a periodic table, the number of protons in the nucleus of the atom increases. Farther the last shell from nucleus, greater is the atom’s size. The atomic size is determined by how far the last shell of electrons is away from the nucleus. Why does the atomic radius increase from right to left? As a result, the atomic radius decreases. The valence electrons are held closer towards the nucleus of the atom. This is because, within a period or family of elements, all electrons are added to the same shell. Why does the atomic radius decrease across a period?Ītomic size gradually decreases from left to right across a period of elements. 4 Are there any exceptions to the atomic radius trend?.3 Why does atomic radius increase as you move down a group?.1 Why does the atomic radius decrease across a period?.

Atomic radius across a period