NEW YORK -- Stocks that traded heavily or had substantial price changes Monday:

       Square Inc., up $25.12 to $272.38.

       The digital payments company is buying Afterpay in an all-stock deal valued at about $29 billion.

       Parker-Hannifin Corp., down $6.57 to $305.46.

       The motion and control technologies company is buying aerospace and defense company Meggitt.

       ON Semiconductor Corp., up $4.58 to $43.64.

       The semiconductor components maker reported strong second-quarter financial results.

       TG Therapeutics Inc., down $7.57 to $27.42.

       The biopharmaceutical company reported disappointing second-quarter financial results.

       Foot Locker Inc., down $1.20 to $55.86.

       The footwear and clothing company is spending more than $1 billion to buy Eurostar and Text Trading Co.

       Caterpillar Inc., down $1.59 to $205.16.

       The construction equipment company slipped along with the broader industrial sector and market.

       Silicon Laboratories Inc., up $6.04 to $155.03.

       The technology company announced a plan to buy back up to $1 billion of its stock.

       Facebook Inc., down $4.35 to $351.95.

       European Union regulators are opening an investigation into the social media company's plan to buy Kustomer.