Question

instructions: in each question, identify the element with the greatest reactivity:

1. titanium (ti), iron (fe), calcium (ca), barium (ba)
2. oxygen (o), carbon (c), nitrogen (n), phosphorus (p)
3. cesium (cs), sodium (na), lithium (li), silver (ag)
4. iodine (i), chlorine (cl), bromine (br), fluorine (f)

Explanation:

Step1: Analyze the reactivity of metals

In the first group (1), among Titanium (Ti), Iron (Fe), Calcium (Ca), Barium (Ba), according to the metal reactivity series \(K>Ca>Na>Mg>Al>Zn>Fe>Sn>Pb>(H)>Cu>Hg>Ag>Pt>Au\), Calcium (\(Ca\)) and Barium (\(Ba\)) are more reactive than \(Ti\) and \(Fe\). And in the periodic table, for Group 2 elements, reactivity increases down the group. Since \(Ba\) is below \(Ca\) in Group 2, \(Ba\) is more reactive than \(Ca\).

Step2: Analyze the reactivity of metals in the second group

In the second group (2), among Oxygen (O), Carbon (C), Nitrogen (N), Phosphorus (P), Oxygen is a non - metal with relatively high reactivity. It readily forms oxides with many elements.

Step3: Analyze the reactivity of metals in the third group

In the third group (3), among Cesium (Cs), Sodium (Na), Lithium (Li), Silver (Ag), according to the metal reactivity series, \(Cs\) is an alkali metal. Alkali metal reactivity increases down the group. \(Cs\) is below \(Na\) and \(Li\) in Group 1, and \(Ag\) is a relatively unreactive metal. So \(Cs\) is the most reactive.

Step4: Analyze the reactivity of non - metals in the fourth group

In the fourth group (4), among Iodine (I), Chlorine (Cl), Bromine (Br), Fluorine (F), for halogens (Group 17 elements), reactivity decreases down the group. Since \(F\) is at the top of Group 17, \(F\) is the most reactive.

Answer:

1. \(Ba\)
2. \(O\)
3. \(Cs\)
4. \(F\)