Question

Arrange the following groups of atoms in order of increasing size. a. Rb, Na, Be b. Sr, Se, Ne c. Fe, P, O

Short answer

The order of increasing atomic size for each group is as follows: a. Be, Na, Rb b. Ne, Se, Sr c. O, P, Fe

Step-by-step solution

Locate the elements on the periodic table

Determine the location of Rb, Na, and Be on the periodic table. Rb (Rubidium) is in Group 1 and Period 5, Na (Sodium) is in Group 1 and Period 3, and Be (Beryllium) is in Group 2 and Period 2.

Apply periodic trends for atomic radius

Recall that atomic size increases going down a group and decreases across a period. Comparing Rb and Na, both in Group 1, Rb is further down the group, so it is larger. Be is in a higher group (Group 2) and a higher period (Period 2), so it is smaller than both Rb and Na.

Arrange in increasing order of size

Based on the analysis in Step 2, the order of increasing atomic size is: Be, Na, Rb. b. Sr, Se, Ne

Locate the elements on the periodic table

Determine the location of Sr, Se, and Ne on the periodic table. Sr (Strontium) is in Group 2 and Period 5, Se (Selenium) is in Group 16 and Period 4, and Ne (Neon) is in Group 18 and Period 2.

Apply periodic trends for atomic radius

Recall that atomic size increases going down a group and decreases across a period. Sr is further down the group and in a lower period compared to Se, so it is larger. Ne is further to the right (higher group number) and at a higher period compared to Se, so it is smaller.

Arrange in increasing order of size

Based on the analysis in Step 2, the order of increasing atomic size is: Ne, Se, Sr. c. Fe, P, O

Locate the elements on the periodic table

Determine the location of Fe, P, and O on the periodic table. Fe (Iron) is in Group 8 and Period 4, P (Phosphorus) is in Group 15 and Period 3, and O (Oxygen) is in Group 16 and Period 2.

Apply periodic trends for atomic radius

Recall that atomic size increases going down a group and decreases across a period. Comparing Fe and P, Fe is in a lower group (lower group number) and a higher period compared to P, so it is larger. Comparing P and O, P is further down the group and in a lower period compared to O, so it is larger.

Arrange in increasing order of size

Based on the analysis in Step 2, the order of increasing atomic size is: O, P, Fe.

Key concepts

Atomic Size

Atomic size, also known as atomic radius, refers to the distance from the nucleus of an atom to the outer boundary of its surrounding cloud of electrons. Understanding atomic size is key to grasping how elements interact with one another.

As you move down a group in the Periodic Table, you'll notice that the atomic size increases. This happens because each subsequent element in a group has an additional electron shell, which makes the atom larger.

In contrast, as you move from left to right across a period, atomic size tends to decrease. This is because electrons are added to the same shell, and the increasing positive charge from the nucleus pulls the electron cloud closer.

It's important to keep these trends in mind. They help us predict the relative sizes of different atoms, which in turn affect things like reactivity, bonding, and electronegativity.

Groups and Periods

The Periodic Table is organized into groups and periods. The vertical columns are called 'groups,' and the horizontal rows are referred to as 'periods.' Each of these arrangements reveals certain patterns in the properties of elements.

Groups contain elements with similar chemical properties because they have the same number of electrons in their outermost shell. For example, Group 1 contains elements that are highly reactive metals like Na and Rb, which share similar characteristics.

Periods, on the other hand, show trends in atomic size and other properties like ionization energy and electronegativity. As you move from left to right across a period, such as from Na to Be, elements become less metallic and more non-metallic in character.

Recognizing these patterns allows scientists and students alike to predict how different elements will behave, making the study of chemistry much more systematic and intuitive.

Periodic Table Analysis

Analyzing the Periodic Table involves looking at the spatial arrangement of elements to deduce trends and make predictions about their behavior. Each element has its unique position, which tells us a lot about its properties.

When analyzing atomic sizes like in the given exercise, understanding the position of an element in its group and period provides critical clues. For example, elements lower down in a group will have larger atomic sizes due to more electron shells. Meanwhile, elements towards the right of a period will have smaller atomic sizes, as the nuclear charge draws the electrons closer.

Another aspect of analysis includes comparing elements from different groups and periods, as demonstrated with Fe, P, and O, where the general trend of decreasing size across a period helps determine their order of size.

By carefully examining these patterns, students can gain insights into not just atomic sizes, but also a wider array of chemical behaviors and interactions.