Answer
Sr is in Group IIA meaning it has 2 valence electrons. It will most likely lose these 2 valence electrons so the preceding shell is a full octet, leaving a charge of 2+.
Ca is in Group IIA meaning it has 2 valence electrons. It will most likely lose these 2 valence electrons so the preceding shell is a full octet, leaving a charge of 2+.
Al is in Group IIIA meaning it has 3 valence electrons. It will most likely lose these 3 valence electrons so the preceding shell is a full octet, leaving a charge of 3+.
Cs is in Group IA meaning it has 1 valence electrons. It will most likely lose this 1 valence electrons so the preceding shell is a full octet, leaving a charge of 1+
Work Step by Step
Sr is in Group IIA meaning it has 2 valence electrons. It will most likely lose these 2 valence electrons so the preceding shell is a full octet, leaving a charge of 2+.
Ca is in Group IIA meaning it has 2 valence electrons. It will most likely lose these 2 valence electrons so the preceding shell is a full octet, leaving a charge of 2+.
Al is in Group IIIA meaning it has 3 valence electrons. It will most likely lose these 3 valence electrons so the preceding shell is a full octet, leaving a charge of 3+.
Cs is in Group IA meaning it has 1 valence electrons. It will most likely lose this 1 valence electrons so the preceding shell is a full octet, leaving a charge of 1+
